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 A368443 #10 Dec 25 2023 10:01:58
%S A368443 1,5,73,1517,42193,1466645,61177753,2977205117,165583073953,
%T A368443 10360379100965,720265883283433,55081115403503117,4595165623000889713,
%U A368443 415299796681103596085,40420990463421954662713,4215173033091627126703517,468870152072269125977393473
%N A368443 Expansion of e.g.f. exp(-x) / (4 - 3*exp(2*x)).
%F A368443 a(n) = (-1)^n + 3 * Sum_{k=1..n} 2^k * binomial(n,k) * a(n-k).
%o A368443 (PARI) a_vector(n) = my(v=vector(n+1)); for(i=0, n, v[i+1]=(-1)^i+3*sum(j=1, i, 2^j*binomial(i, j)*v[i-j+1])); v;
%Y A368443 Cf. A367977, A368442, A368454.
%K A368443 nonn
%O A368443 0,2
%A A368443 _Seiichi Manyama_, Dec 24 2023