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 A068481 #20 Jun 06 2022 05:47:35 %S A068481 5,9,21,33,65,81,89,113,173,209,221,245,261,281,285,309,341,345,369, %T A068481 393,473,509,525,545,561,593,645,725,749,785,789,833,861,873,933,953, %U A068481 965,1001,1065,1101,1113,1173,1185,1265,1289,1329,1341,1401,1409,1469 %N A068481 Numbers k such that gcd(k!+1, 2^k+1) > 1. %H A068481 Amiram Eldar, <a href="/A068481/b068481.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from G. C. Greubel) %p A068481 select(n->gcd(factorial(n)+1,2^n+1)>1,[$1..1470]); # _Muniru A Asiru_, Oct 16 2018 %t A068481 Select[Range[2500], GCD[#! + 1, 2^# + 1] > 1 &] (* _G. C. Greubel_, Oct 15 2018 *) %o A068481 (PARI) isok(n) = gcd(n!+1,2^n+1) > 1; \\ _Michel Marcus_, Oct 16 2018 %o A068481 (GAP) Filtered([1..1470],n->Gcd(Factorial(n)+1,2^n+1)>1); # _Muniru A Asiru_, Oct 16 2018 %Y A068481 Cf. A000051 (2^n+1), A038507 (n!+1). %Y A068481 Cf. A068480, A068482, A068483. %K A068481 easy,nonn %O A068481 1,1 %A A068481 _Benoit Cloitre_, Mar 10 2002