A366119 Expansion of (1/x) * Series_Reversion( x*(1+x+x^3)/(1+x)^5 ).
1, 4, 22, 139, 950, 6831, 50899, 389402, 3040433, 24127641, 194015198, 1577355740, 12943616840, 107061667210, 891666351501, 7471125565836, 62932782325745, 532621542290355, 4526846632642489, 38621126867786485, 330635368752515710, 2839444812305017875
Offset: 0
Keywords
Links
- Seiichi Manyama, Table of n, a(n) for n = 0..1000
Programs
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PARI
a(n) = sum(k=0, n\3, (-1)^k*binomial(n+k, k)*binomial(4*n-k+4, n-3*k))/(n+1);
Formula
a(n) = (1/(n+1)) * Sum_{k=0..floor(n/3)} (-1)^k * binomial(n+k,k) * binomial(4*n-k+4,n-3*k).