A145327 - OEIS

A145327

Least k such that f(n,k) is not a prime, where f(n,1)=4n+1 and f(n,k)=f(f(n,k-1)) for k>=2.

%I #2 Mar 30 2012 18:57:11

%S 2,1,3,2,1,1,2,1,3,2,1,1,2,1,2,1,1,3,1,1,1,2,1,3,2,1,2,2,1,1,1,1,1,2,

%T 1,1,2,1,2,1,1,1,2,1,2,1,1,3,2,1,1,1,1,1,1,1,2,2,1,2,1,1,1,2,1,1,2,1,

%U 3,2,1,1,2,1,1,1,1,2,2,1,1,1,1,2,1,1,2,2,1,1,1,1,2,1,1,1,2,1,2,2,1,2,1,1,2

%N Least k such that f(n,k) is not a prime, where f(n,1)=4n+1 and f(n,k)=f(f(n,k-1)) for k>=2.

%e f(1,1)=5, f(1,2)=21, so a(1)=2.

%e f(2,1)=9, so a(2)=1.

%e f(3,1)=13, f(3,2)=53, f(3,3)=213, so a(3)=3.

%Y Cf. A145325, A145326.

%K easy,nonn

%O 1,1

%A _Clark Kimberling_, Oct 07 2008