A373904 - OEIS

A373904

a(n) = Sum_{k=0..floor(n/2)} binomial(n+4*k,n-2*k).

1, 1, 2, 8, 30, 98, 303, 937, 2936, 9260, 29209, 91999, 289547, 911255, 2868341, 9029425, 28424456, 89478064, 281667368, 886657848, 2791106585, 8786123349, 27657838272, 87064092870, 274068969337, 862741412709, 2715822822365, 8549136056237, 26911817257385

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OFFSET

0,3

LINKS

Table of n, a(n) for n=0..28.

Index entries for linear recurrences with constant coefficients, signature (6,-14,20,-15,6,-1).

FORMULA

a(n) = 6*a(n-1) - 14*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6).

G.f.: 1/(1 - x - x^2/(1 - x)^5).

PROG

(PARI) a(n) = sum(k=0, n\2, binomial(n+4*k, n-2*k));

CROSSREFS