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 A368438 #13 Dec 25 2023 10:02:19
%S A368438 1,5,49,725,14305,352805,10441489,360526325,14226677185,631571457605,
%T A368438 31152937452529,1690317145051925,100052040656540065,
%U A368438 6415726051515362405,443047566486308303569,32780692416679034537525,2587108326603274903810945
%N A368438 Expansion of e.g.f. exp(x) / (3 - 2*exp(2*x)).
%F A368438 a(n) = 1 + 2 * Sum_{k=1..n} 2^k * binomial(n,k) * a(n-k).
%o A368438 (PARI) a_vector(n) = my(v=vector(n+1)); for(i=0, n, v[i+1]=1+2*sum(j=1, i, 2^j*binomial(i, j)*v[i-j+1])); v;
%Y A368438 Cf. A080253, A337026, A368439.
%Y A368438 Cf. A368442.
%K A368438 nonn
%O A368438 0,2
%A A368438 _Seiichi Manyama_, Dec 24 2023