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 A145325 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. 2

%I

%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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Last modified May 20 05:35 EDT 2019. Contains 323417 sequences. (Running on oeis4.)