A110709 Nonprimes of the form n*(n-1)^n - 1.

1, 323, 93749, 1959551, 46118407, 1207959551, 37661140520651, 1390911669927935, 55123269399790045, 2333521433367183359, 105094533691406249999, 5017514388048998039551, 13456471561751415850795007, 751799469150919163867112019

Offset

1,2

Comments

If n = 3, then 3*2^3 - 1 = 23 is prime, so 23 is not in this sequence.

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..100

Example

a(1) = 1 = 2*1^2 - 1.
a(2) = 323 = 4*3^4 - 1.

Mathematica

Select[Table[n (n - 1)^n - 1, {n, 2, 20}], ! PrimeQ[#] &] (* Vincenzo Librandi, Mar 22 2014 *)

Prog

(Magma) [a: n in [2..40] | not IsPrime(a) where a is n*(n-1)^n-1]; // Vincenzo Librandi, Jun 13 2011

Crossrefs

Cf. A191699, A191715.

Sequence in context: A210056 A202984 A346387 * A298271 A006465 A272298

Adjacent sequences: A110706 A110707 A110708 * A110710 A110711 A110712

Keyword

nonn

Author

Juri-Stepan Gerasimov, Jun 13 2011

Extensions

Corrected and extended by Vincenzo Librandi, Jun 13 2011

Status

approved