A375314 a(n) = Sum_{k=0..floor(n/2)} binomial(4*k,n-2*k).
1, 0, 1, 4, 7, 12, 30, 68, 137, 292, 644, 1380, 2936, 6324, 13625, 29216, 62701, 134784, 289547, 621708, 1335378, 2868620, 6161329, 13233352, 28424456, 61053608, 131135696, 281665480, 604991601, 1299461088, 2791106585, 5995016764, 12876698159, 27657841516
Offset: 0
Links
- Index entries for linear recurrences with constant coefficients, signature (0,1,4,6,4,1).
Crossrefs
Cf. A116090.
Programs
-
PARI
a(n) = sum(k=0, n\2, binomial(4*k, n-2*k));
-
PARI
my(N=40, x='x+O('x^N)); Vec(1/(1-x^2*(1+x)^4))
Formula
a(n) = a(n-2) + 4*a(n-3) + 6*a(n-4) + 4*a(n-5) + a(n-6).
G.f.: 1/(1 - x^2*(1 + x)^4).