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A073443 Numbers n such that n! - n - 1 is prime. 3
3, 4, 10, 12, 346 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Clearly n <> 2 (mod 3). For n>3, n!-n, n!-n+1, ..., n!-3, n!-2 is a sequence of n-1 consecutive composite numbers. Additional terms are greater than 2000.

LINKS

Table of n, a(n) for n=1..5.

MATHEMATICA

Select[Range[3, 346], PrimeQ[#! - # - 1] &] (* Arkadiusz Wesolowski, Jan 04 2012 *)

PROG

(PARI) for(n=3, 2000, if(isprime(n!-n-1), print1(n, ", ")))

CROSSREFS

Cf. A073444 (corresponding primes), A002982 (n!-1 is prime), A073308 (n!+n+1 is prime).

Sequence in context: A092434 A239632 A031367 * A257494 A302347 A092119

Adjacent sequences:  A073440 A073441 A073442 * A073444 A073445 A073446

KEYWORD

nonn,more

AUTHOR

Rick L. Shepherd, Jul 31 2002

EXTENSIONS

Offset corrected by Arkadiusz Wesolowski, Jan 04 2012

STATUS

approved

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Last modified November 14 14:50 EST 2018. Contains 317208 sequences. (Running on oeis4.)