A360087 a(n) = Sum_{k=0..n} (-1)^k * binomial(3*k,n-k).
1, -1, -2, 2, 6, -5, -17, 12, 48, -28, -135, 63, 378, -134, -1054, 259, 2927, -408, -8096, 280, 22305, 1551, -61210, -10638, 167310, 46683, -455489, -175852, 1234960, 612380, -3334215, -2031953, 8962498, 6523626, -23981046, -20445373, 63855135, 62900496
Offset: 0
Links
- Index entries for linear recurrences with constant coefficients, signature (-1,-3,-3,-1).
Programs
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PARI
a(n) = sum(k=0, n, (-1)^k*binomial(3*k, n-k));
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PARI
my(N=40, x='x+O('x^N)); Vec(1/(1+x*(1+x)^3))
Formula
a(n) = -a(n-1) - 3*a(n-2) - 3*a(n-3) - a(n-4).
G.f.: 1/(1 + x*(1+x)^3).