A291846 - OEIS

%I #11 Sep 03 2017 16:58:23

%S 1,1,5,33,283,2995,37723,551047,9157923,170606547,3521075919,

%T 79741123539,1965955092517,52414187219485,1502559229282213,

%U 46087421890091145,1506033038595292467,52232959640093489043,1916263566511685329711,74142047814365044902307,3017192203838382727894241,128829022389463544587355721,5758871157244067281788041809

%N Central terms in irregular triangle A291845.

%C 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.

%H Paul D. Hanna, <a href="/A291846/b291846.txt">Table of n, a(n) for n = 0..300</a>

%F a(n) = A291845(n,n).

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

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

%o {for(n=0,25,print1(A291845(n,n),", "))}

%Y Cf. A291845, A291847, A291848.

%K nonn

%O 0,3

%A _Paul D. Hanna_, Sep 03 2017