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 A367839 #8 Dec 02 2023 08:12:55
%S A367839 1,2,17,183,2679,48903,1071621,27394965,800378019,26307021483,
%T A367839 960739737777,38595129840369,1691405818822719,80301792637126791,
%U A367839 4105701241574252445,224912022483008478141,13142159127790633537947,815924005186398537216483
%N A367839 Expansion of e.g.f. 1/(2 + x - exp(3*x)).
%F A367839 a(0) = 1; a(n) = -n * a(n-1) + Sum_{k=1..n} 3^k * binomial(n,k) * a(n-k).
%o A367839 (PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=-i*v[i]+sum(j=1, i, 3^j*binomial(i, j)*v[i-j+1])); v;
%Y A367839 Cf. A032032, A367838, A367840.
%Y A367839 Cf. A367785, A367836.
%K A367839 nonn
%O A367839 0,2
%A A367839 _Seiichi Manyama_, Dec 02 2023