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 A377510 #7 Nov 04 2024 22:30:03
%S A377510 1,2,1,3,1,6,1,2,1,1,5,4,1,1,1,1,1,2,4,1,4,3,1,1,2,1,2,1,2,1,1,1,1,3,
%T A377510 1,3,1,2,1,1,1,5,1,1,1,1,1,1,1,2,1,1,2,1,1,1,1,2,1,1,2,1,2,1,2,1,1,1,
%U A377510 1,1,1,1,4,2,1,1,1,1,1,2,1,1,1,1,2,1
%N A377510 a(n) = number of iterations of x -> 2 x + 5 to reach a nonprime, starting with prime(n).
%C A377510 See A377120 for a guide to related sequences.
%e A377510 prime(6) = 13 -> 31 -> 67 -> 139 -> 283 -> 571 -> 1147 = 31*37, so a(6) = 6.
%t A377510 Table[p = Prime[n]; c = 1; While[p = 2*p + 5; PrimeQ[p], c++]; c, {n, 200}]
%Y A377510 Cf. A377120, A377511, A377512, A377513, A377514.
%K A377510 nonn
%O A377510 1,2
%A A377510 _Clark Kimberling_, Oct 31 2024