A369513 Expansion of (1/x) * Series_Reversion( x * ((1-x)^3-x^2)^2 ).
1, 6, 59, 704, 9317, 131534, 1940819, 29572146, 461725783, 7348829928, 118788308725, 1944758772450, 32180850839619, 537370617961928, 9043679909643500, 153238910560266234, 2612067747321247779, 44760267182734834916, 770626480741892413249
Offset: 0
Keywords
Programs
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PARI
my(N=20, x='x+O('x^N)); Vec(serreverse(x*((1-x)^3-x^2)^2)/x) -
PARI
a(n) = sum(k=0, n\2, binomial(2*n+k+1, k)*binomial(7*n+k+5, n-2*k))/(n+1);
Formula
a(n) = (1/(n+1)) * Sum_{k=0..floor(n/2)} binomial(2*n+k+1,k) * binomial(7*n+k+5,n-2*k).