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A215096
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a(0)=0, a(1)=1, a(n) = n! - a(n-2).
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3
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0, 1, 2, 5, 22, 115, 698, 4925, 39622, 357955, 3589178, 39558845, 475412422, 6187461955, 86702878778, 1301486906045, 20836087009222, 354385941189955, 6381537618718778, 121290714467642045, 2426520470557921222, 50969651457241797955, 1121574207307049758778
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OFFSET
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0,3
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LINKS
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FORMULA
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D-finite with recurrence a(n) -n*a(n-1) +a(n-2) -n*a(n-3)=0. - R. J. Mathar, Jun 04 2021
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MAPLE
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a:= proc(n) a(n):= `if`(n<2, n, n! - a(n-2)) end:
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MATHEMATICA
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nxt[{n_, a_, b_}]:={n+1, b, (n+1)!-a}; NestList[nxt, {1, 0, 1}, 30][[;; , 2]] (* Harvey P. Dale, Feb 15 2024 *)
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PROG
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(Python)
prpr = 0
prev = f = 1
for n in range(2, 33):
print prpr,
f *= n
curr = f - prpr
prpr = prev
prev = curr
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CROSSREFS
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Cf. A005165: a(0) = 0, a(n) = n! - a(n-1).
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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