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A110525 Expansion of 1/(1-x^2*c(3x)), c(x) the g.f. A000108. 2
1, 0, 1, 3, 19, 141, 1180, 10593, 99712, 971067, 9702388, 98899638, 1024429861, 10752006033, 114097140757, 1222113460332, 13195550763793, 143470913825427, 1569448022488435, 17261100136608984, 190752895126918819 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

Diagonal sums of A110518.

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..930

FORMULA

a(n) = Sum_{k=0..floor(n/2)} (k/(n-k))*C(2*n-3*k-1, n-2*k)*3^(n-2*k).

MATHEMATICA

Join[{1}, Table[Sum[(k/(n - k))*Binomial[2*n - 3*k - 1, n - 2*k]*3^(n - 2*k), {k, 0, Floor[n/2]}], {n, 1, 50}]] (* G. C. Greubel, Aug 30 2017 *)

PROG

(PARI) concat([1], for(n=1, 25, print1(sum(k=0, n\2, (k/(n - k))*binomial(2*n - 3*k - 1, n - 2*k)*3^(n - 2*k)), ", "))) \\ G. C. Greubel, Aug 30 2017

CROSSREFS

Sequence in context: A025571 A221266 A082758 * A058859 A291964 A095002

Adjacent sequences:  A110522 A110523 A110524 * A110526 A110527 A110528

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Jul 24 2005

STATUS

approved

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Last modified June 20 19:33 EDT 2019. Contains 324234 sequences. (Running on oeis4.)