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 A117210 #20 Mar 25 2018 06:42:47
%S A117210 1,1,-1,-2,0,1,1,0,-1,-1,2,1,-2,-3,2,4,2,-5,-4,0,5,2,1,-5,-1,2,5,-5,
%T A117210 -2,-2,5,-1,3,-6,2,0,11,-6,-4,-10,12,-1,6,-13,5,-8,16,-8,9,-13,17,-17,
%U A117210 7,-21,25,-10,22,-29,20,-24,34,-24,27,-44,35,-32,39,-52,45,-39,66,-53,47,-76,70,-55,79,-98,66,-84,115,-89
%N A117210 G.f. A(x) satisfies (1+x) = product_{n>=1} A(x^n).
%C A117210 Self-convolution inverse is A117211.
%H A117210 Vaclav Kotesovec, <a href="/A117210/b117210.txt">Table of n, a(n) for n = 0..10000</a> (terms 0..1000 from Paul D. Hanna)
%H A117210 N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>
%F A117210 G.f.: A(x) = exp( Sum_{n>=1} A117212(n)*x^n/n ).
%F A117210 G.f.: A(x) = product_{k>=1}(1 + x^k)^mu(k) where mu(k) is the Möbius function, A008683 - _Stuart Clary_, Apr 15 2006
%F A117210 Weigh transform of A008683(n). - _Vladeta Jovovic_, Apr 20 2006
%t A117210 nmax = 81; CoefficientList[ Series[ Product[ (1 + x^k)^(MoebiusMu[k]), {k, 1, nmax} ], {x, 0, nmax} ], x ] (* _Stuart Clary_, Apr 15 2006 *)
%o A117210 (PARI) {a(n)=if(n==0,1,if(n==1,1, -polcoeff(prod(i=1,n,sum(k=0,min(n\i,n-1),a(k)*x^(i*k))+x*O(x^n)),n,x)))}
%Y A117210 Cf. A117212 (l.g.f.), A117211 (inverse); variants: A117208, A117209.
%K A117210 sign,look
%O A117210 0,4
%A A117210 _Paul D. Hanna_, Mar 03 2006