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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
| 1,1
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REFERENCES
| 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. [J. V. Post was a student of Herbert John Ryser (1923-1985) at Caltech.]
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LINKS
| R. M. Dickau, Derangement diagrams.
H. Fripertinger, The Recontre Numbers, an online calculator.
Mehdi Hassani, Derangements and Applications, Journal of Integer Sequences, Vol. 6 (2003), #03.1.2
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FORMULA
| a(0) = 2 because !0 + 1 = 2.
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EXAMPLE
| a(5) = 130850092279663 because the 5+1 = 6th subfactorial prime is !17 - 1 = 130850092279664 - 1 = 130850092279663, which is prime. a(0) = a(1) = 2 because !0 = !2 = 1, so !0 + 1 = !2 + 1 = 2.
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CROSSREFS
| Cf. A000166.
Sequence in context: A162712 A062581 A077520 * A042819 A100443 A060415
Adjacent sequences: A100012 A100013 A100014 * A100016 A100017 A100018
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KEYWORD
| nonn
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AUTHOR
| Jonathan Vos Post (jvospost3(AT)gmail.com), Nov 18 2004
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