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A061062
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Sum of squared factorials: (0!)^2 + (1!)^2 + (2!)^2 + (3!)^2 +...+ (n!)^2.
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9
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1, 2, 6, 42, 618, 15018, 533418, 25935018, 1651637418, 133333531818, 13301522971818, 1606652445211818, 231049185247771818, 39006837228880411818, 7639061293780877851818, 1717651314017980301851818
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OFFSET
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0,2
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COMMENTS
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There is a Kurepa-like conjecture (see A049782) for this sequence: for primes p>3, p does not divide a(p-1). However, the conjecture fails for p=20879. - T. D. Noe, Dec 08 2004
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LINKS
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FORMULA
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Recurrence: a(0) = 1, a(1) = 2, a(n) = (n^2+1)*a(n-1) - n^2*a(n-2). - Vladimir Reshetnikov, Oct 28 2015
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EXAMPLE
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a(2) = 0!*0! + 1!*1! + 2!*2! = 6.
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MAPLE
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MATHEMATICA
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s=0; Table[s=s+(n!)^2, {n, 0, 20}]
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PROG
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(PARI) { a=0; for (n=0, 100, write("b061062.txt", n, " ", a+=(n!)^2) ) } \\ Harry J. Smith, Jul 17 2009
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CROSSREFS
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KEYWORD
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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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