Generalized Fermat Primes sorted by base

A prime number of the form b^(2^n) + 1 is called a generalized Fermat prime. Here we give a list of such primes sorted by base b.

Exponents n
b=2 0, 1, 2, 3, 4, ...
b=4 Please see under b=2
b=6 0, 1, 2, ...
b=8 Impossible since 8=2^3
b=10 0, 1, ...
b=12 0, ...
b=14 1, ...
b=16 Please see under b=2
b=18 0, ...
b=20 1, 2, ...
b=22 0, ...
b=24 1, 2, ...
b=26 1, ...
b=28 0, 2, ...
b=30 0, 5, ...
b=32 Impossible since 32=2^5
b=34 2, ...
b=36 Please see under b=6
b=38 ...
b=40 0, 1, ...
b=42 0, ...
b=44 4, ...
b=46 0, 2, 9, ...
b=48 2, ...
b=50 ...
b=52 0, ...
b=54 1, 2, 5, ...
b=56 1, 2, ...
b=58 0, ...
b=60 0, ...
b=62 ...
b=64 Impossible since 64=4^3
b=66 0, 1, ...
b=68 ...
b=70 0, ...
b=72 0, ...
b=74 1, 2, 4, ...
b=76 4, ...
b=78 0, ...
b=80 2, ...
b=82 0, 2, ...
b=84 1, ...
b=86 ...
b=88 0, 2, ...
b=90 1, 2, ...
b=92 ...
b=94 1, 4, ...
b=96 0, 5, ...
b=98 ...
b=100 Please see under b=10
b=102 0, 6, ...
b=104 ...
b=106 0, 2, ...
b=108 0, ...
b=110 1, ...
b=112 0, 5, ...
b=114 5, ...
b=116 1, ...
b=118 2, 3, ...
b=120 1, 7, ...
b=122 ...
b=124 1, ...
b=126 0, 1, ...
b=128 Impossible since 128=2^7
b=130 0, 1, ...
b=132 2, 3, 5, ...
b=134 1, ...
b=136 0, ...
b=138 0, ...
b=140 2, 3, ...
b=142 2, ...
b=144 Please see under b=12
b=146 1, ...
b=148 0, ...
b=150 0, 1, 11, ...
b=152 3, ...
b=154 2, ...
b=156 0, 1, 4, 5, ...
b=158 4, ...
b=160 1, 2, ...
b=162 0, 6, ...
b=164 2, ...
b=166 0, ...
b=168 ...
b=170 1, ...
b=172 0, ...
b=174 2, ...
b=176 1, 4, ...
b=178 0, ...
b=180 0, 1, 2, ...
b=182 ...
b=184 1, ...
b=186 ...
b=188 4, ...
b=190 0, 7, ...
b=192 0, ...
b=194 2, ...
b=196 Please see under b=14
b=198 0, 2, 4, ...
b=200 ...
b=202 ...
b=204 1, 2, ...
b=206 1, ...
b=208 3, ...
b=210 0, 1, 2, ...
b=212 ...
b=214 ...
b=216 Impossible since 216=6^3
b=218 ...
b=220 2, ...
b=222 0, ...
b=224 1, ...
b=226 0, ...
b=228 0, 2, ...
b=230 1, ...
b=232 0, ...
b=234 7, ...
b=236 1, ...
b=238 0, 2, ...
b=240 0, 1, 3, ...
b=242 2, 3, ...
b=244 ...
b=246 ...
b=248 2, 4, ...
b=250 0, 1, ...
b=252 ...
b=254 2, ...
b=256 Please see under b=2
b=258 ...
b=260 1, ...
b=262 0, ...
b=264 1, ...
b=266 2, ...
b=268 0, ...
b=270 0, 1, ...
b=272 2, ...
b=274 6, ...
b=276 0, 2, ...
b=278 2, 8, ...
b=280 0, 1, ...
b=282 0, ...
b=284 1, ...
b=286 ...
b=288 2, 3, 4, ...
b=290 3, ...
b=292 0, ...
b=294 ...
b=296 2, ...
b=298 ...
b=300 1, 6, ...
b=302 ...
b=304 ...
b=306 0, 1, 3, 4, ...
b=308 ...
b=310 0, ...
b=312 0, 2, ...
b=314 1, ...
b=316 0, ...
b=318 4, ...
b=320 2, ...
b=322 ...
b=324 Please see under b=18
b=326 1, ...
b=328 2, ...
b=330 0, 4, ...
b=332 5, ...
b=334 2, ...
b=336 0, ...
b=338 ...
b=340 1, 2, ...
b=342 5, ...
b=344 ...
b=346 0, ...
b=348 0, 4, ...
b=350 1, ...
b=352 0, 2, ...
b=354 ...
b=356 ...
b=358 0, ...
b=360 5, ...
b=362 ...
b=364 2, ...
b=366 0, ...
b=368 ...
b=370 4, ...
b=372 0, ...
b=374 2, ...
b=376 5, ...
b=378 0, 3, ...
b=380 ...
b=382 0, 4, ...
b=384 1, ...
b=386 1, ...
b=388 0, ...
b=390 ...
b=392 3, ...
b=394 ...
b=396 0, 1, 4, ...
b=398 ...
b=400 Please see under b=20
b=402 ...
b=404 ...
b=406 1, ...
b=408 0, ...
b=410 ...
b=412 6, ...
b=414 2, ...
b=416 ...
b=418 0, ...
b=420 0, 1, ...
b=422 ...
b=424 ...
b=426 3, ...
b=428 5, ...
b=430 0, 1, 2, 5, ...
b=432 0, 5, ...
b=434 3, ...
b=436 1, 2, ...
b=438 0, ...
b=440 1, ...
b=442 0, 2, 3, ...
b=444 1, ...
b=446 ...
b=448 0, 5, ...
b=450 ...
b=452 4, ...
b=454 ...
b=456 0, 4, ...
b=458 ...
b=460 0, ...
b=462 0, ...
b=464 1, ...
b=466 0, 1, 2, ...
b=468 ...
b=470 1, 4, ...
b=472 2, ...
b=474 1, 4, ...
b=476 2, 4, ...
b=478 0, 4, ...
b=480 ...
b=482 ...
b=484 Please see under b=22
b=486 0, ...
b=488 2, ...
b=490 0, 1, ...
b=492 2, ...
b=494 2, ...
b=496 1, ...
b=498 0, 2, ...
b=500 ...
b=502 0, ...
b=504 2, ...
b=506 7, ...
b=508 0, 3, ...
b=510 3, ...
b=512 Impossible since 512=8^3
b=514 ...
b=516 2, ...
b=518 ...
b=520 0, ...
b=522 0, ...
b=524 ...
b=526 2, ...
b=528 ...
b=530 ...
b=532 7, ...
b=534 ...
b=536 1, ...
b=538 ...
b=540 0, 2, 3, ...
b=542 3, ...
b=544 1, ...
b=546 0, ...
b=548 7, ...
b=550 2, ...
b=552 ...
b=554 2, ...
b=556 0, 1, 2, ...
b=558 ...
b=560 4, ...
b=562 0, 3, 5, 6, ...
b=564 ...
b=566 2, ...
b=568 0, 2, 4, ...
b=570 0, 1, ...
b=572 ...
b=574 ...
b=576 Please see under b=24
b=578 ...
b=580 ...
b=582 2, ...
b=584 1, 2, ...
b=586 0, ...
b=588 5, ...
b=590 ...
b=592 0, 6, ...
b=594 1, ...
b=596 3, ...
b=598 0, 4, ...
b=600 0, 2, ...
b=602 ...
b=604 ...
b=606 0, ...
b=608 ...
b=610 3, ...
b=612 0, ...
b=614 8, ...
b=616 0, 2, ...
b=618 0, ...
b=620 ...
b=622 ...
b=624 2, ...
b=626 ...
b=628 2, ...
b=630 0, ...
b=632 ...
b=634 1, ...
b=636 1, ...
b=638 ...
b=640 0, ...
b=642 0, 4, ...
b=644 1, ...
b=646 0, 1, ...
b=648 ...
b=650 ...
b=652 0, ...
b=654 1, ...
b=656 2, ...
b=658 0, ...
b=660 0, ...
b=662 ...
b=664 3, ...
b=666 ...
b=668 ...
b=670 ...
b=672 0, ...
b=674 1, ...
b=676 Please see under b=26
b=678 ...
b=680 1, 3, ...
b=682 0, 3, ...
b=684 ...
b=686 1, 4, ...
b=688 4, ...
b=690 0, 1, 2, 4, ...
b=692 ...
b=694 ...
b=696 1, ...
b=698 ...
b=700 0, 1, ...
b=702 2, ...
b=704 1, ...
b=706 ...
b=708 0, ...
b=710 2, ...
b=712 ...
b=714 1, ...
b=716 1, ...
b=718 0, ...
b=720 ...
b=722 ...
b=724 ...
b=726 0, 5, ...
b=728 6, ...
b=730 2, ...
b=732 0, 2, 3, ...
b=734 ...
b=736 4, ...
b=738 0, 2, 5, ...
b=740 1, ...
b=742 0, 2, ...
b=744 ...
b=746 ...
b=748 2, ...
b=750 0, 1, ...
b=752 ...
b=754 ...
b=756 0, ...
b=758 2, ...
b=760 0, 1, 2, ...
b=762 ...
b=764 1, ...
b=766 ...
b=768 0, 2, ...
b=770 ...
b=772 0, 2, ...
b=774 4, ...
b=776 4, ...
b=778 2, 4, ...
b=780 1, ...
b=782 3, ...
b=784 Please see under b=28
b=786 0, 2, ...
b=788 2, ...
b=790 4, ...
b=792 ...
b=794 ...
b=796 0, ...
b=798 2, ...
b=800 2, 3, ...
b=802 ...
b=804 5, ...
b=806 ...
b=808 0, 3, ...
b=810 0, 2, ...
b=812 ...
b=814 ...
b=816 1, ...
b=818 ...
b=820 0, ...
b=822 0, ...
b=824 10, ...
b=826 0, 1, ...
b=828 0, ...
b=830 4, ...
b=832 4, ...
b=834 4, ...
b=836 ...
b=838 0, ...
b=840 ...
b=842 ...
b=844 ...
b=846 4, ...
b=848 ...
b=850 5, ...
b=852 0, ...
b=854 ...
b=856 0, 2, ...
b=858 0, ...
b=860 1, ...
b=862 0, ...
b=864 1, ...
b=866 3, ...
b=868 ...
b=870 ...
b=872 ...
b=874 2, ...
b=876 0, 3, ...
b=878 ...
b=880 0, ...
b=882 0, ...
b=884 3, 5, ...
b=886 0, ...
b=888 ...
b=890 1, ...
b=892 3, 8, ...
b=894 2, ...
b=896 ...
b=898 8, ...
b=900 Please see under b=30
b=902 ...
b=904 ...
b=906 0, 1, ...
b=908 ...
b=910 0, 1, ...
b=912 2, ...
b=914 2, ...
b=916 3, 4, ...
b=918 0, 3, ...
b=920 1, ...
b=922 ...
b=924 ...
b=926 ...
b=928 0, 2, ...
b=930 1, 2, ...
b=932 ...
b=934 3, ...
b=936 0, 1, 2, ...
b=938 ...
b=940 0, ...
b=942 ...
b=944 ...
b=946 0, 1, 4, ...
b=948 ...
b=950 1, ...
b=952 0, 2, ...
b=954 ...
b=956 3, 4, ...
b=958 ...
b=960 1, 7, ...
b=962 2, ...
b=964 ...
b=966 0, 1, 2, ...
b=968 ...
b=970 0, ...
b=972 4, ...
b=974 ...
b=976 0, ...
b=978 ...
b=980 ...
b=982 0, 4, ...
b=984 4, ...
b=986 1, 2, ...
b=988 ...
b=990 0, 3, ...
b=992 2, ...
b=994 ...
b=996 0, 2, ...
b=998 ...
b=1000 Impossible since 1000=10^3

(Colored cells correspond to Sloane's A075090.)

Ellipsis (dots) means that no more terms are known. It does not necessarily imply that the sequence continues. One can conjecture that every row in the above table is a finite sequence.

There are several ways to define new integer sequences from the above table: Concatenate all rows. Or give number of terms in each row. Or list row numbers whose sequences are empty. None of these sequences appear in Sloane's. But since there may be terms not yet discovered in each row, it is probably best not to submit these sequences.

First b for which n occurs in the row: A056993

First b for which all of 0, 1, 2, ..., n occur in the row: A090872

Greatest known values of n

The following table is inspired by Yves Gallot's pages (old version). Here we give the greatest known values of n. Please note that new primes may have been discovered after this page was updated.

Currently known bases b OEIS
n>22   (none)
n=22 2^n=4194304 (none)
n=21 2^n=2097152 2524190
n=20 2^n=1048576 919444, 1059094, 1951734, 1963736, 3843236 A321323
n=19 2^n=524288 75898, 341112, 356926, 475856, 1880370, 2061748, 2312092, 2733014, 2788032, 2877652, and more A243959
n=18 2^n=262144 24518, 40734, 145310, 361658, 525094, 676754, 773620, 1415198, 1488256, 1615588, and more A244150
n=17 2^n=131072 62722, 130816, 228188, 386892, 572186, 689186, 909548, 1063730, 1176694, 1361244, and more A253854
n=16 2^n=65536 48594, 108368, 141146, 189590, 255694, 291726, 292550, 357868, 440846, 544118, and more A251597
n=15 2^n=32768 70906, 167176, 204462, 249830, 321164, 330716, 332554, 429370, 499310, 524552, and more A226530
n=14 2^n=16384 67234, 101830, 114024, 133858, 162192, 165306, 210714, 216968, 229310, 232798, and more A226529
n=13 2^n=8192 30406, 71852, 85654, 111850, 126308, 134492, 144642, 147942, 150152, 165894, and more A226528
n=12 2^n=4096 1534, 7316, 17582, 18224, 28234, 34954, 41336, 48824, 51558, 51914, and more A088362
n=11 2^n=2048 150, 2558, 4650, 4772, 11272, 13236, 15048, 23302, 26946, 29504, and more A088361
n=10 2^n=1024 824, 1476, 1632, 2462, 2484, 2520, 3064, 3402, 3820, 4026, and more A057002
n=9 2^n=512 46, 1036, 1318, 1342, 2472, 2926, 3154, 3878, 4386, 4464, and more A057465
n=8 2^n=256 278, 614, 892, 898, 1348, 1494, 1574, 1938, [2116], 2122, 2278, and more A056995
n=7 2^n=128 120, 190, 234, 506, 532, 548, 960, 1738, 1786, 2884, and more A056994
n=6 2^n=64 102, 162, 274, 300, 412, 562, 592, 728, 1084, 1094, and more A006316
n=5 2^n=32 30, 54, 96, 112, 114, 132, 156, 332, 342, 360, and more A006315
n=4 2^n=16 2, 44, 74, 76, 94, 156, 158, 176, 188, 198, and more A006313
n=3 2^n=8 2, [4], 118, 132, 140, 152, 208, 240, 242, 288, 290, and more A006314
n=2 2^n=4 2, [4], 6, [16], 20, 24, 28, 34, 46, 48, 54, 56, and more A000068
n=1 2^n=2 2, [4], 6, 10, 14, [16], 20, 24, 26, [36], 40, 54, 56, and more A005574
n=0 2^n=1 2, [4], 6, 10, 12, [16], 18, 22, 28, 30, [36], 40, 42, and more A006093

In the above table, there is no guarantee the bases shown are the smallest possible.

See:


/JeppeSN