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A100015
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Subfactorial primes: primes of the form !n + 1 or !n - 1. Subfactorial or rencontres numbers or derangements !n = A000166.
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2
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OFFSET
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1,1
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COMMENTS
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No additional terms through n <= 2000. (* Harvey P. Dale, Feb 17 2023 *)
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REFERENCES
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R. A. Brualdi and H. J. Ryser: Combinatorial Matrix Theory, 1992, Section 7.2, p. 202.
H. J. Ryser, Combinatorial Mathematics. Mathematical Association of America, Carus Mathematical Monograph 14, 1963, p. 23.
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LINKS
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EXAMPLE
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a(5) = 130850092279663 because the 5th subfactorial prime is !17 - 1 = 130850092279664 - 1 = 130850092279663. a(1) = 2 because !0 = !2 = 1, so !0 + 1 = !2 + 1 = 2.
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MATHEMATICA
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Select[Union[Flatten[Table[Subfactorial[n]+{1, -1}, {n, 20}]]], PrimeQ] (* Harvey P. Dale, Feb 17 2023 *)
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CROSSREFS
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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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