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A307663 a(n) = (n-1)!*(Sum_{i=1..n} Sum_{j=1..i} binomial(i,j)*i/j). 0
1, 6, 41, 329, 3090, 33654, 420792, 5981688, 95782320, 1712555280, 33909364800, 737868052800, 17521164259200, 451126883894400, 12522623670144000, 372847351488998400, 11853064556660275200, 400718191717647820800, 14354714544806716416000, 543129329390299739136000, 21642934280974058207232000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..21.

EXAMPLE

a(2) = 1! * (C(1,1)*1/1 + C(2,1)*2/1 + C(2,2)*2/2) = 6.

MATHEMATICA

Array[(# - 1)!*Sum[Sum[Binomial[i, j] i/j, {j, i}], {i, #}] &, 21] (* Michael De Vlieger, Apr 21 2019 *)

PROG

(PARI) a(n) = (n-1)!*sum(i=1, n, sum(j=1, i, binomial(i, j)*i/j)); \\ Michel Marcus, Apr 20 2019

CROSSREFS

Sequence in context: A095177 A199553 A225031 * A083430 A005011 A187814

Adjacent sequences:  A307660 A307661 A307662 * A307664 A307665 A307666

KEYWORD

nonn

AUTHOR

Pedro Caceres, Apr 20 2019

STATUS

approved

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Last modified September 27 20:35 EDT 2020. Contains 337388 sequences. (Running on oeis4.)