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A007912
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Quantum factorials: (n-1)!! - (n-2)!! (mod n).
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4
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1, 1, 0, 1, 5, 1, 0, 1, 2, 3, 0, 1, 0, 1, 0, 9, 2, 15, 0, 1, 2, 9, 0, 1, 0, 7, 0, 15, 2, 1, 0, 1, 0, 27, 0, 1, 0, 25, 0, 21, 2, 11, 0, 1, 45, 33, 0, 25, 0, 39, 0, 27, 0, 49, 0, 1, 57, 15, 0, 1, 0, 1, 0, 33, 2, 51, 0, 35, 2, 9, 0, 1, 0, 19, 0, 39, 77, 65, 0, 1, 81, 63, 0, 1, 0, 33, 0, 45, 0
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OFFSET
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3,5
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REFERENCES
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S. P. Hurd and J. S. McCranie, Quantum factorials. Proceedings of the Twenty-fifth Southeastern International Conference on Combinatorics, Graph Theory and Computing (Boca Raton, FL, 1994). Congr. Numer. 104 (1994), 19-24.
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LINKS
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FORMULA
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a(n) = 0 iff n is odd and not a prime congruent to 3 modulo 4. - Charlie Neder, Feb 24 2019
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MAPLE
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a:= n-> (d-> irem(d(n-1)-d(n-2), n))(doublefactorial):
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MATHEMATICA
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Table[Mod[(n-1)!!-(n-2)!!, n], {n, 3, 100}] (* Harvey P. Dale, Aug 07 2012 *)
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CROSSREFS
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KEYWORD
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nonn,easy,nice
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AUTHOR
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STATUS
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approved
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