This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A321577 #20 Dec 06 2021 11:01:44 %S A321577 0,2,5,2,5,17,5,2,257,17,5,17,5,17,257,2,5,1025,5,65537,257,17,5, %T A321577 65537,129,17,67108865,65537,5,17,5,2,257,17,262145,268435457,5,17, %U A321577 257,65537,5,4194305,5,65537,131073,17,5,65537,1073741825,16777217,257,65537,5 %N A321577 a(n) = F_n mod M_n, where F_n = 2^(2^n) + 1 and M_n = 2^n - 1. %C A321577 Sequence contains all Fermat numbers > 3. %H A321577 Antti Karttunen, <a href="/A321577/b321577.txt">Table of n, a(n) for n = 1..3344</a> %F A321577 For n > 1, a(n) = 2^(2^n mod n) + 1 = A112987(n) + 1. %t A321577 Prepend[1 + 2^Array[PowerMod[2, #, #] &, 85, 2], 0] (* _Michael De Vlieger_, Nov 13 2018, after _Vincenzo Librandi_ at A112987 *) %o A321577 (PARI) apply( A321577(n)=if(n>1,2^lift(Mod(2, n+!n)^n)+1), [0..50]) \\ _M. F. Hasler_, Nov 19 2018 %Y A321577 Cf. A000215, A000225, A112987. %K A321577 nonn %O A321577 1,2 %A A321577 _Thomas Ordowski_, Nov 13 2018