A377514 - OEIS

%I #4 Nov 13 2024 17:26:35

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

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

%U 4,3,2,1,1,3,1,2,1,1,1,2,1,1,1,2,1,3

%N a(n) = number of iterations of x -> 2 x - 7 to reach a nonprime, starting with  prime(n+4).

%C See A377120 for a guide to related sequences.

%e prime(6) = 13 -> 19 -> 31 -> 55 = 5*11, so a(2) = 3.

%t Table[p = Prime[n + 4]; c = 1; While[p = 2*p - 7; PrimeQ[p], c++]; c, {n, 200}

%Y Cf. A377120, A377510, A377511, A377512, A377513.

%K nonn

%O 1,2

%A _Clark Kimberling_, Nov 05 2024