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 A055510 #20 Feb 16 2025 08:32:42
%S A055510 0,0,5,0,5,5,17,0,17,5,17,5,13,17,53,0,17,17,29,5,0,17,53,5,29,13,
%T A055510 1619,17,29,53,1619,0,29,17,53,17,37,29,101,5,1619,0,43,17,17,53,1619,
%U A055510 5,37,29,29,13,53,1619,1619,17,43,29,101,53,61,1619,1619,0,37,29,101,17,13
%N A055510 Largest odd prime in sequence obtained in 3x+1 (or Collatz) problem starting at n, or 0 if no such prime is found.
%H A055510 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CollatzProblem.html">Collatz Problem</a>
%H A055510 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a>
%t A055510 op[n_]:=Module[{lst=NestWhileList[If[EvenQ[#],#/2,3#+1]&,n,#!=1&],m}, m= Max[Select[ lst,PrimeQ]];If[m<3,0,m]]; Array[op,70] (* _Harvey P. Dale_, Apr 30 2011 *)
%Y A055510 Cf. A055509, A087272.
%K A055510 nonn
%O A055510 1,3
%A A055510 _G. L. Honaker, Jr._, Jun 30 2000
%E A055510 More terms from Larry Reeves (larryr(AT)acm.org), Aug 09 2001