A291847 - OEIS

A291847

A diagonal of irregular triangle A291845.

1, 4, 26, 224, 2389, 30324, 446109, 7460928, 139775763, 2899264620, 65954625560, 1632654953280, 43688087178059, 1256602120453484, 38661480001233486, 1266934683224418816, 44054989554206606603, 1620147926716343851500, 62826169539072988352134, 2562071016044926371845920, 109611597248567432265872903, 4908887251696851858305862332

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OFFSET

0,2

COMMENTS

G.f. of row n in triangle A291845 equals Product_{k=0..n-1} (1 + (2*k+1)*x + x^2), with row sums equal to the odd double factorials A001147.

LINKS

Paul D. Hanna, Table of n, a(n) for n = 0..300

FORMULA

a(n) = A291845(n+1,n).

PROG

(PARI) /* As a Diagonal in Triangle A291845 */

{A291845(n, k)=polcoeff(prod(j=0, n-1, 1 + (2*j+1)*x + x^2), k)}