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A301423
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Numbers k such that !k/(k-1) is prime, where !k = A000166(k) is the subfactorial of k.
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0
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OFFSET
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1,1
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COMMENTS
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Also numbers k such that A000255(k-2) is prime.
The corresponding primes are 3, 11, 53, 1468457, 34361893981, 22742406079421034331584846001936724930824184898296683, ...
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LINKS
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MATHEMATICA
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Select[Range[2, 100], PrimeQ[Subfactorial[#]/(#-1)] &]
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PROG
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(PARI) isok(n) = (n != 1) && isprime(n!*sum(k=0, n, (-1)^k/k!)/(n-1)); \\ Michel Marcus, Mar 24 2018
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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