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 A087966 #8 Sep 23 2018 20:57:10 %S A087966 1,1,1,1,1,9,1,1,1,1,1,9,1,1,1,1,1,27,1,25,49,1,1,9,1,1,1,1,1,9,1,1,1, %T A087966 1,1,27,1,1,1,25,1,441,1,1,1,1,1,9,1,1,1,1,1,81,1,1,1,1,1,225,1,1,49, %U A087966 1,1,9,1,1,1,1,1,27,1,1,1,1,1,9,1,25,1,1,1,441,1,1,1,1,1,27,1,1,1,1,1,9,1,1 %N A087966 a(n) = gcd(-1 + 2^n, n^2). %H A087966 Antti Karttunen, <a href="/A087966/b087966.txt">Table of n, a(n) for n = 1..65537</a> %e A087966 a(6) = gcd(2^6 - 1,6^2) = gcd(64-1,36) = 9. %p A087966 seq(gcd(2^n-1,n^2),n=1..120); # _Muniru A Asiru_, Sep 22 2018 %o A087966 (PARI) A087966(n) = gcd((2^n)-1, n^2); \\ _Antti Karttunen_, Sep 22 2018 %o A087966 (GAP) List([1..120],n->Gcd(2^n-1,n^2)); # _Muniru A Asiru_, Sep 22 2018 %Y A087966 Cf. A087967, A087968. %K A087966 nonn %O A087966 1,6 %A A087966 _Labos Elemer_, Sep 22 2003