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 A368014 #9 Dec 08 2023 09:57:12
%S A368014 1,-2,0,22,-48,-722,5160,39142,-731808,-1875362,138079320,-428616938,
%T A368014 -32571174768,360902614798,8748630825480,-218739750924218,
%U A368014 -2165282730308928,135578968355309758,-45942716160492360,-89526354705694434698,1011199293695966345712
%N A368014 Expansion of e.g.f. 1/(1 - exp(x) + exp(3*x)).
%F A368014 a(0) = 1; a(n) = Sum_{k=1..n} (1 - 3^k) * binomial(n,k) * a(n-k).
%o A368014 (PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=sum(j=1, i, (1-3^j)*binomial(i, j)*v[i-j+1])); v;
%Y A368014 Cf. A355408, A355410.
%K A368014 sign
%O A368014 0,2
%A A368014 _Seiichi Manyama_, Dec 08 2023