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 A087968 #8 Sep 23 2018 20:57:17 %S A087968 1,1,9,1,1,1,1,1,27,25,1,1,1,1,9,1,1,1,1,1,9,1,1,1,1,1,81,1,1,25,1,1, %T A087968 9,1,1,1,1,1,9,1,1,1,1,1,27,1,1,1,1,125,9,1,1,1,121,1,9,1,1,1,1,1,27, %U A087968 1,1,1,1,289,9,25,1,1,1,1,9,1,1,169,1,1,243,1,1,1,1,1,9,1,1,25,1,1,9,1,1,1 %N A087968 a(n) = gcd(1 + 2^n, n^2). %H A087968 Antti Karttunen, <a href="/A087968/b087968.txt">Table of n, a(n) for n = 1..65537</a> %e A087968 a(9) = gcd(2^9 + 1,9^2) = gcd(513,81) = 27. %p A087968 seq(gcd(2^n+1,n^2),n=1..100); # _Muniru A Asiru_, Sep 22 2018 %o A087968 (PARI) A087968(n) = gcd((2^n)+1, n^2); \\ _Antti Karttunen_, Sep 22 2018 %o A087968 (GAP) List([1..100],n->Gcd(2^n+1,n^2)); # _Muniru A Asiru_, Sep 22 2018 %Y A087968 Cf. A087966, A087969. %K A087968 nonn %O A087968 1,3 %A A087968 _Labos Elemer_, Sep 22 2003