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A108879 Numbers n such that (n-1)*n^n+1 is prime. 1
2, 4, 20, 93, 100, 1536 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..6.

EXAMPLE

2 is in the sequence because (2-1)*2^2+1 = 1*2^2+1 = 4+1 = 5, which is prime.

MATHEMATICA

Select[Range[1000], PrimeQ[(# - 1) #^# + 1] &] (* Vincenzo Librandi, Oct 23 2014 *)

PROG

(PARI) isok(n) = isprime((n-1)*n^n+1); \\ Michel Marcus, Oct 23 2014

(MAGMA) [n: n in [1..1000] |IsPrime((n-1)*n^n+1)]; // Vincenzo Librandi, Oct 23 2014

CROSSREFS

Cf. A108318.

Sequence in context: A325791 A188326 A158094 * A341855 A337038 A058006

Adjacent sequences:  A108876 A108877 A108878 * A108880 A108881 A108882

KEYWORD

hard,more,nonn

AUTHOR

Ray G. Opao, Jul 14 2005

STATUS

approved

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Last modified July 25 03:53 EDT 2021. Contains 346283 sequences. (Running on oeis4.)