A368438 Expansion of e.g.f. exp(x) / (3 - 2*exp(2*x)).
1, 5, 49, 725, 14305, 352805, 10441489, 360526325, 14226677185, 631571457605, 31152937452529, 1690317145051925, 100052040656540065, 6415726051515362405, 443047566486308303569, 32780692416679034537525, 2587108326603274903810945
Offset: 0
Keywords
Programs
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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;
Formula
a(n) = 1 + 2 * Sum_{k=1..n} 2^k * binomial(n,k) * a(n-k).