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A175411
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a(n) = Sum_{i=(n*n-n+2)/2..(n*n+n)/2} i!.
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0
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1, 8, 864, 4037040, 1401598598400, 53652268264218624000, 316196664157721349185863680000, 382630662500715988102392981826830336000000, 122342346998826334909002798912467017444232685158400000000, 12931604174610554670466196146308122246477496321113350463375278080000000000
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OFFSET
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1,2
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LINKS
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EXAMPLE
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a(4) = 7! + 8! + 9! + 10! = 4037074.
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PROG
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(PARI) a(n)= sum(i=(n^2-n+2)/2, (n^2+n)/2, i!); \\ Michel Marcus, Mar 15 2022
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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