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 A086372 #7 Jul 02 2025 16:02:02 %S A086372 -1,0,1,-1,1,-1,1,0,0,0,0,1,-1,1,0,1,-1,1,0,1,0,0,1,1,0,0,2,0,1,0,2,1, %T A086372 1,0,3,1,1,1,3,2,1,2,3,3,2,2,4,5,1,4,5,5,3,5,6,7,4,6,8,9,5,8,11,10,8, %U A086372 10,13,13,11,12,17,17,13,16,22,19,19,20,26,26,23,25,33,32,29 %N A086372 First differences of A027349. %C A086372 Sequence has the same parity as A000041, the partition numbers, i.e. a(n) is congruent A040051(n) mod 2 (proved by _James Sellers_ using generating functions). %o A086372 (PARI) a(n)=polcoeff((1-x)*prod(k=1,n,1+x^(2*k+1),1+x*O(x^n)),n) %K A086372 sign,easy %O A086372 1,27 %A A086372 _Ralf Stephan_, Sep 06 2003