A370801 Expansion of (1/x) * Series_Reversion( x/(x+1/(1-x+x^4)) ).
1, 2, 5, 15, 50, 176, 638, 2351, 8735, 32523, 120707, 444218, 1611211, 5714056, 19578953, 63495983, 186784641, 442718804, 396470087, -4588483661, -45923198497, -305945783479, -1761810468901, -9395726622973, -47743575327196, -234512941253088, -1122653095777562
Offset: 0
Keywords
Programs
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PARI
my(N=30, x='x+O('x^N)); Vec(serreverse(x/(x+1/(1-x+x^4)))/x)
Formula
a(n) = Sum_{k=0..n} binomial(n,k) * b(k), where g.f. B(x) = Sum_{k>=0} b(k)*x^k satisfies B(x) = (1/x) * Series_Reversion( x*(1-x+x^4) ).