This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A377120 #6 Nov 04 2024 22:28:52
%S A377120 4,1,4,3,1,3,2,2,1,2,1,1,1,3,6,2,1,1,6,1,2,1,1,2,5,1,1,1,1,3,2,1,5,2,
%T A377120 1,1,2,1,3,3,1,1,1,2,4,2,1,2,2,2,1,1,1,1,1,1,2,1,4,1,2,1,5,1,1,1,1,2,
%U A377120 1,2,2,1,1,1,2,2,1,3,1,2,1,1,1,1,2,1
%N A377120 a(n) = number of iterations of x -> 2 x + 3 to reach a nonprime, starting with prime(n) .
%C A377120 Guide to related sequences:
%C A377120 mapping initial prime sequence
%C A377120 x -> 2x + 1 2 A181697
%C A377120 x -> 2x + 3 2 this sequence
%C A377120 x -> 2x + 5 2 A377510
%C A377120 x -> 2x + 7 2 A377511
%C A377120 x -> 2x - 1 2 A181715
%C A377120 x -> 2x - 3 5 A377512
%C A377120 x -> 2x - 5 11 A377513
%C A377120 x -> 2x - 7 11 A377514
%e A377120 prime(1) = 2 -> 7 -> 17 -> 37 -> 77 = 7*11, so a(1) = 4.
%t A377120 Table[p = Prime[n]; c = 1; While[p = 2*p + 3; PrimeQ[p], c++]; c, {n, 200}]
%Y A377120 Cf. A000040, A181697, A181715, A377510, A377511, A377512, A377513, A377514.
%K A377120 nonn
%O A377120 1,1
%A A377120 _Clark Kimberling_, Oct 31 2024