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A157829 Numbers k such that k! - (k-1)! + (k-2)! + 1 is prime. 0
2, 5, 7, 11, 13, 16, 22, 29, 43, 56, 67, 83, 85, 107, 317, 325, 517, 1660, 2010, 2368, 4483, 4697 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..22.

EXAMPLE

a(11) = 11! - 10! + 9! + 1 = 36650881 (prime).

a(16) = 16! - 15! + 14! + 1 = 19702293811201 (prime).

MAPLE

a := proc (n) if isprime(factorial(n-2)*((n-1)^2+1)+1) = true then n else end if end proc: seq(a(n), n = 2 .. 700); # Emeric Deutsch, Mar 18 2009

PROG

(PARI) is(n)=ispseudoprime(1+(n^2-2*n+2)*(n-2)!) \\ Charles R Greathouse IV, Dec 27 2013

(PFGW) ABC2 $a!-($a-1)!+($a-2)!+1

a: from 2 to 10000

Charles R Greathouse IV, Dec 27 2013

CROSSREFS

Sequence in context: A191406 A322969 A229470 * A020581 A081259 A177512

Adjacent sequences:  A157826 A157827 A157828 * A157830 A157831 A157832

KEYWORD

nonn

AUTHOR

Kyle D. Balliet, Mar 07 2009

EXTENSIONS

More terms from Emeric Deutsch, Mar 18 2009

a(18)-a(22) from Charles R Greathouse IV, Dec 27 2013

STATUS

approved

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Last modified September 23 22:32 EDT 2020. Contains 337315 sequences. (Running on oeis4.)