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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

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

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.)