A291846 - OEIS

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A291846

Central terms in irregular triangle A291845.

1, 1, 5, 33, 283, 2995, 37723, 551047, 9157923, 170606547, 3521075919, 79741123539, 1965955092517, 52414187219485, 1502559229282213, 46087421890091145, 1506033038595292467, 52232959640093489043, 1916263566511685329711, 74142047814365044902307, 3017192203838382727894241, 128829022389463544587355721, 5758871157244067281788041809

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OFFSET

0,3

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,n).

PROG

(PARI) /* As Central Terms of Triangle A291845 */

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