1,1

If n == 5 mod 6 (A016969), k^n + k - 1 is always divisible by k^2 - k + 1. Thus it will never be prime.

Table of n, a(n) for n=1..81.

(PARI) a(n)=if(n==Mod(5, 6), return(0)); k=1; while(!isprime(k^n+k-1), k++); k

vector(100, n, a(n))

Cf. A016969, A045546, A236475, A236759, A113517.

Sequence in context: A292372 A098008 A234808 * A127638 A127639 A248081

Adjacent sequences: A248076 A248077 A248078 * A248080 A248081 A248082

nonn

Derek Orr, Sep 30 2014

approved