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 A384974 #7 Jun 14 2025 10:37:23 %S A384974 1,1,3,8,25,57,22,-1003,-9967,-67627,-394013,-1958808,-7869346, %T A384974 -17261270,104411359,1931214493,19188604691,153913872501, %U A384974 1080677292567,6709916699425,35489004465351,135918792966633,-9832967202556,-7535958768199373,-106301159541342282 %N A384974 G.f. A(x) satisfies A(x) = 1 + x*A(x)/A(-x*A(x)^3)^2. %F A384974 See A384977. %o A384974 (PARI) a(n, k=-1) = if(n*k==0, 0^n, (-1)^n*k*sum(j=1, n, binomial(-3*n+3*j+k-1, j-1)*a(n-j, 2*j)/j)); %Y A384974 Column k=1 of A384977. %K A384974 sign %O A384974 0,3 %A A384974 _Seiichi Manyama_, Jun 14 2025