A221476 Prime numbers having no additional odd primes in their Collatz (3x+1) trajectory.

2, 5, 113, 227, 2417, 3637, 7253, 14549, 14563, 30559, 38677, 38833, 155333, 206923, 207121, 217309, 464213, 466033, 620771, 827693, 915737, 1100149, 1100353, 1220983, 1303873, 1472893, 1656901, 1963813, 2327483, 2475797, 2933717, 2933731, 3313777, 3491083

Offset: 1

Author

T. D. Noe, Feb 14 2013

Keywords

• nonn

Comments

Sequence A221475 contains odd composite numbers with this property.

Links

• Index entries for sequences related to 3x+1 (or Collatz) problem

Crossrefs

Cf. A221475.

Programs

Mathematica

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; t = {}; n = 0; While[Length[t] < 50, n++; p = Prime[n]; If[Union[Drop[PrimeQ[Rest[Collatz[p]]], -2]] == {False}, AppendTo[t, p]]]; t