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 A385015 #12 Jun 15 2025 09:57:29 %S A385015 1,1,4,4,-13,-81,-389,-198,7455,44515,198661,70243,-5428624,-40239313, %T A385015 -218619844,-408542577,3648305171,44441073999,339489511573, %U A385015 1430556904456,2122222427956,-35048613488679,-504238969376070,-3684488832562182,-21342732340391295,-67688326964892247 %N A385015 G.f. A(x) satisfies A(x) = 1 + x*A(x)/A(-x*A(x))^3. %F A385015 See A385019. %o A385015 (PARI) a(n, k=-1) = if(n*k==0, 0^n, (-1)^n*k*sum(j=1, n, binomial(-n+j+k-1, j-1)*a(n-j, 3*j)/j)); %Y A385015 Column k=1 of A385019. %Y A385015 Cf. A384951, A385014, A385016. %Y A385015 Cf. A213231, A213232, A384975. %Y A385015 Cf. A384896. %K A385015 sign %O A385015 0,3 %A A385015 _Seiichi Manyama_, Jun 15 2025