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A175411
a(n) = Sum_{i=(n*n-n+2)/2..(n*n+n)/2} i!.
0
1, 8, 864, 4037040, 1401598598400, 53652268264218624000, 316196664157721349185863680000, 382630662500715988102392981826830336000000, 122342346998826334909002798912467017444232685158400000000, 12931604174610554670466196146308122246477496321113350463375278080000000000
OFFSET
1,2
EXAMPLE
a(4) = 7! + 8! + 9! + 10! = 4037074.
PROG
(PARI) a(n)= sum(i=(n^2-n+2)/2, (n^2+n)/2, i!); \\ Michel Marcus, Mar 15 2022
CROSSREFS
Cf. A000142.
Sequence in context: A097818 A360195 A262379 * A027725 A265239 A375892
KEYWORD
easy,nonn
AUTHOR
Ctibor O. Zizka, May 07 2010
EXTENSIONS
a(4) corrected and more terms from Michel Marcus, Mar 15 2022
STATUS
approved