A129243 - OEIS

%I #6 Sep 24 2019 02:39:59

%S 2,2,4,2,40,6,24,14,6,14,32,54,30,108,40,110,120,182,374,20,114,2,84,

%T 80,80,110,36,78,68,200,26,228,30,12,82,294,102,530,36,98,618,2,108,

%U 734,672,404,114,458,1102,42,154,362,998,30,58,404,28,72,434,132,266,2,308

%N Least K such that K*(prime(n)^n)-1 is prime with prime(n)=n-th prime.

%e 2*(2^1)-1=3 prime so a(1)=2;

%e 2*(3^2)-1=17 prime so a(2)=2;

%e 4*(5^3)-1=2499 prime so a(3)=4;

%e 2*(7^4)-1=4801 prime so a(4)=2.

%o (PARI) a(n) = {my(k=2, x=prime(n)^n); while (!isprime(k*x-1), k+=2); k;} \\ _Michel Marcus_, Sep 24 2019

%Y Cf. A129244, A129245.

%K nonn

%O 1,1

%A _Pierre CAMI_, Apr 05 2007