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 A118812 Primes of the form (2n)! - n! + 1. 8
 2, 23, 87178286161, 403291461126605629356979201, 5502622159812088949850305428800254867109635014075023360001 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The next term, if it exists, has more than 7500 digits. - M. F. Hasler, Feb 09 2014 Primes in sequence A237580 = n -> (2n)! - n! + 1, i.e., the terms of that sequence which coincide with A237579(n) = least prime factor of (2n)! - n! + 1. - M. F. Hasler, Feb 09 2014 REFERENCES G. Balzarotti and P. P. Lava, Le sequenze di numeri interi, Hoepli, 2008, p. 159. LINKS FORMULA A118812 = A237580 o A237443 = A237579 o A237443. - M. F. Hasler, Feb 09 2014 EXAMPLE For n=2, (2*2)! - 2! + 1 = 24 - 2 + 1 = 23, which is prime. MAPLE PFACT:=proc(N) local i, r; for i from 1 by 1 to N do r:=(2*i)!-i!+1; if isprime(r) then print(i); fi; od; end: PFACT(100); MATHEMATICA Select[Table[(2n)!-n!+1, {n, 30}], PrimeQ] (* Harvey P. Dale, May 05 2018 *) PROG (PARI) for(n=1, 999, ispseudoprime(p=(2*n)!-n!+1)&&print1(p", ")) \\ M. F. Hasler, Feb 09 2014 CROSSREFS Cf. A237443 (corresponding values of n). Sequence in context: A334616 A089987 A162605 * A228241 A054909 A171636 Adjacent sequences:  A118809 A118810 A118811 * A118813 A118814 A118815 KEYWORD nonn AUTHOR Paolo P. Lava and Giorgio Balzarotti, May 23 2006 STATUS approved

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Last modified January 21 01:15 EST 2021. Contains 340332 sequences. (Running on oeis4.)