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 A135864 #7 Jun 18 2025 13:14:38 %S A135864 1,9,27,0,-81,243,0,-2916,10935,0,-168399,682344,0,-11711385,49364964, %T A135864 0,-900438201,3887490915,0,-73729998576,323480165085,0,-6303914878248, %U A135864 27978933759300,0,-556251967191492,2490404893915293,0,-50276620111538700,226626845346291663,0 %N A135864 G.f. A(x) satisfies A(x) = 1 + 9*x*A(x)^(1/3). %F A135864 a(n) = -9^n*binomial(n/3,n)/(2n/3 - 1). %F A135864 G.f. A(x) satisfies A(x) = 1/A(-x*A(x)^(-1/3)). - _Seiichi Manyama_, Jun 18 2025 %o A135864 (PARI) a(n)=9^n*binomial(n/3,n)/(1-2*n/3) %Y A135864 Cf. A135863, A135866, A214668. %K A135864 sign %O A135864 0,2 %A A135864 _Paul D. Hanna_, Dec 02 2007