A368790 a(n) = (3*n-2)!!! * Sum_{k=0..n} 1/(3*k-2)!!!.

1, 2, 9, 64, 641, 8334, 133345, 2533556, 55738233, 1393455826, 39016763129, 1209519657000, 41123668338001, 1521575728506038, 60863029140241521, 2617110253030385404, 120387071639397728585, 5898966510330488700666, 306746258537185412434633

Offset

0,2

Links

Table of n, a(n) for n=0..18.

Formula

a(n) = (3*n-2) * a(n-1) + 1.

Prog

(PARI) a007559(n) = prod(k=1, n, 3*k-2);
a(n) = a007559(n)*sum(k=0, n, 1/a007559(k));

Crossrefs

Row sums of A136214.

Cf. A007559, A112293, A368791.

Sequence in context: A112319 A232552 A038038 * A048801 A395120 A152915

Adjacent sequences: A368787 A368788 A368789 * A368791 A368792 A368793

Keyword

nonn,easy

Author

Seiichi Manyama, Jan 05 2024

Status

approved