A055510 Largest odd prime in sequence obtained in 3x+1 (or Collatz) problem starting at n, or 0 if no such prime is found.

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, 1619, 17, 29, 53, 1619, 0, 29, 17, 53, 17, 37, 29, 101, 5, 1619, 0, 43, 17, 17, 53, 1619, 5, 37, 29, 29, 13, 53, 1619, 1619, 17, 43, 29, 101, 53, 61, 1619, 1619, 0, 37, 29, 101, 17, 13

Offset: 1

Author

G. L. Honaker, Jr., Jun 30 2000

Keywords

• nonn

Links

• Eric Weisstein's World of Mathematics, Collatz Problem
• Index entries for sequences related to 3x+1 (or Collatz) problem

Crossrefs

Cf. A055509, A087272.

Programs

Mathematica

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 *)

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), Aug 09 2001