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A217284

a(n) = Sum_{k=0..n} (n!/k!)^3.

1, 2, 17, 460, 29441, 3680126, 794907217, 272653175432, 139598425821185, 101767252423643866, 101767252423643866001, 135452212975869985647332, 234061424022303335198589697, 514232948577000427431301564310, 1411055210895289172871491492466641, 4762311336771600958441283787074913376

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OFFSET

0,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..180

FORMULA

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

a(n) ~ 2.12970254898330641813452361... * (n!)^3 = A271574 * (n!)^3.

a(n) = n^3 * a(n-1) + 1. - Seiichi Manyama, May 02 2021

MATHEMATICA

Table[Sum[(n!/k!)^3, {k, 0, n}], {n, 0, 20}]

PROG