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A321948 Column k=3 of triangle A257673. 3
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified April 14 10:14 EDT 2021. Contains 342949 sequences. (Running on oeis4.)