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 A368895 #9 Jan 09 2024 08:48:09
%S A368895 1,1,1,-2,-7,-14,13,113,337,19,-2579,-10867,-9911,71852,431229,741181,
%T A368895 -2178783,-20081708,-51012467,58414532,1061935641,3651310699,1841181,
%U A368895 -62090909433,-279070619279,-250335322449,3913178936941,22877592319648,38634162528361
%N A368895 a(n) = Sum_{k=0..floor(n/3)} (-n)^k * binomial(n-2*k,k).
%F A368895 a(n) = [x^n] 1/(1 - x + n*x^3).
%o A368895 (PARI) a(n) = sum(k=0, n\3, (-n)^k*binomial(n-2*k, k));
%Y A368895 Cf. A368891, A368894.
%K A368895 sign,easy
%O A368895 0,4
%A A368895 _Seiichi Manyama_, Jan 09 2024