%I #2 Mar 30 2012 18:57:11
%S 3,5,2,1,4,2,1,2,2,1,3,1,1,3,2,1,1,2,1,4,2,1,2,1,1,3,1,1,2,2,1,1,2,1,
%T 2,2,1,1,2,1,3,1,1,5,1,1,1,2,1,2,2,1,2,2,1,3,1,1,1,1,1,1,2,1,3,1,1,2,
%U 2,1,1,1,1,2,2,1,1,2,1,1,2,1,2,1,1,3,1,1,4,2,1,1,1,1,3,2,1,2,2,1,1,1,1,1,2
%N Least k such that f(n,k) is not a prime, where f(n,1)=2n+1 and f(n,k)=f(f(n,k-1)) for k>=2.
%e f(1,1)=3, f(1,2)=7, f(1,3)=15, so a(1)=3.
%e For n=1,2,3,4,5, the first few f's follow:
%e 1: 3,7,15,31,63
%e 2: 5,11,23,47,95
%e 3: 7,15,31,63,127
%e 4: 9,19,39,77,159
%e 5: 11,23,47,95,191
%Y Cf. A145326, A145327.
%K easy,nonn
%O 1,1
%A _Clark Kimberling_, Oct 07 2008
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