A366054 Expansion of (1/x) * Series_Reversion( x*(1-x)^2/(1-x+x^4) ).
1, 1, 2, 5, 15, 49, 168, 594, 2149, 7919, 29627, 112254, 429884, 1661308, 6470678, 25375070, 100106145, 397018815, 1582005849, 6330533220, 25428891084, 102497788194, 414445390730, 1680617637425, 6833083703094, 27849689394894, 113762630541908
Offset: 0
Keywords
Programs
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PARI
a(n) = sum(k=0, n\4, binomial(n+1, k)*binomial(2*n-3*k, n-4*k))/(n+1);
Formula
a(n) = (1/(n+1)) * Sum_{k=0..floor(n/4)} binomial(n+1,k) * binomial(2*n-3*k,n-4*k).