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 A214669 #6 Aug 22 2024 16:45:50
%S A214669 1,-4,36,-720,29264,-2370368,379341376,-119616350464,74306729686272,
%T A214669 -91021121260127232,220137897341768508416,-1052620193410626774192128,
%U A214669 9963741205378506824566067200,-186912918064963001770860269879296,6955904583765468148520677987319955456
%N A214669 a(n) = Sum_{k=1..n*(n+1)/2} k * A214670(n,k).
%o A214669 (PARI) {a(n)=local(A214670=x*y); A214670=sum(m=1, n, -x^m*prod(j=1, m, (1-(1+y)^j)/(1-x*(1+y)^j))+x*O(x^n)); polcoeff(subst(deriv(A214670,y),y,1), n, x)}
%o A214669 for(n=1, 25, print1(a(n),", "))
%Y A214669 Cf. A214670.
%K A214669 sign
%O A214669 1,2
%A A214669 _Paul D. Hanna_, Jul 25 2012