A391326 - OEIS

A391326

Expansion of g/(1 + x^3*g^3), where g = 1+x*g^4 is the g.f. of A002293.

1, 1, 4, 21, 136, 947, 6945, 52858, 413697, 3308796, 26925841, 222227383, 1855755034, 15651109359, 133121828588, 1140609311220, 9835711615762, 85295338371581, 743396385161313, 6508187266161161, 57206828084607355, 504679861263048121, 4467036428134316648

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OFFSET

0,3

LINKS

Seiichi Manyama, Table of n, a(n) for n = 0..1000

FORMULA

a(n) = Sum_{k=0..floor(n/3)} (-1)^k * (3*k+1) * binomial(4*n-9*k+1,n-3*k)/(4*n-9*k+1).

PROG

(PARI) a(n) = sum(k=0, n\3, (-1)^k*(3*k+1)*binomial(4*n-9*k+1, n-3*k)/(4*n-9*k+1));

CROSSREFS

Cf. A002293, A391100.

Sequence in context: A205077 A292928 A367047 * A209881 A288869 A288268

Adjacent sequences: A391323 A391324 A391325 * A391327 A391328 A391329

KEYWORD

nonn

AUTHOR

Seiichi Manyama, Dec 07 2025

STATUS

approved