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 A367043 #12 Nov 03 2023 11:20:24 %S A367043 1,1,4,23,144,997,7304,55646,436320,3497846,28538852,236203518, %T A367043 1978290648,16735471979,142789868112,1227339581084,10617748941840, %U A367043 92377468226466,807769888050640,7095187345173620,62574408414192220,553881698543850337 %N A367043 G.f. satisfies A(x) = 1 + x^3 + x*A(x)^4. %F A367043 a(n) = Sum_{k=0..floor(n/3)} binomial(3*(n-3*k)+1,k) * binomial(4*(n-3*k),n-3*k)/(3*(n-3*k)+1). %o A367043 (PARI) a(n) = sum(k=0, n\3, binomial(3*(n-3*k)+1, k)*binomial(4*(n-3*k), n-3*k)/(3*(n-3*k)+1)); %Y A367043 Cf. A366676, A367042. %K A367043 nonn %O A367043 0,3 %A A367043 _Seiichi Manyama_, Nov 03 2023