A321948 Column k=3 of triangle A257673.

1, 9, 45, 174, 576, 1719, 4761, 12441, 31050, 74593, 173547, 392787, 867876, 1877322, 3984636, 8314434, 17082510, 34604523, 69194309, 136709688, 267111510, 516515227, 989147760, 1877103486, 3531796959, 6591644601, 12208734552, 22449066710, 40995144288

Offset

3,2

Links

Alois P. Heinz, Table of n, a(n) for n = 3..5000

Formula

G.f.: (-1 + Product_{k>=1} 1 / (1 - x^k)^k)^3. - Ilya Gutkovskiy, Jan 30 2021

Maple

b:= proc(n, k) option remember; `if`(n=0, 1, k*add(
      b(n-j, k)*numtheory[sigma][2](j), j=1..n)/n)
    end:
a:= n-> (k-> add(b(n, k-i)*(-1)^i*binomial(k, i), i=0..k))(3):
seq(a(n), n=3..35);

Crossrefs

Column k=3 of A257673.

Sequence in context: A276280 A036826 A022574 * A050574 A124647 A111640

Adjacent sequences: A321945 A321946 A321947 * A321949 A321950 A321951

Keyword

nonn

Author

Alois P. Heinz, Nov 22 2018

Status

approved