A354227 Odd numbers whose Collatz trajectory contains exactly 12 odd numbers.

39, 79, 153, 157, 305, 307, 315, 317, 611, 613, 629, 631, 647, 683, 687, 1221, 1229, 1241, 1257, 1261, 1265, 1269, 1295, 1353, 1367, 1369, 1375, 1505, 2445, 2453, 2481, 2483, 2489, 2507, 2515, 2517, 2521, 2525, 2531, 2545, 2589, 2593, 2633, 2705, 2707, 2733

Offset

1,1

Links

Table of n, a(n) for n=1..46.

Formula

{ A005408 } intersect { A072122 }.

Example

305 is a term since its Collatz trajectory is 305, 916, 458, 229, 688, 344, 172, 86, 43, 130, 65, 196, 98, 49, 148, 74, 37, 112, 56, 28, 14, 7, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1.

Mathematica

q[n_] := Count[NestWhileList[If[OddQ[#], 3 # + 1, #/2] &, n, # > 1 &], _?OddQ] == 12; Select[Range[1, 2750, 2], q] (* Amiram Eldar, May 20 2022 *)

Crossrefs

Cf. A005408, A072122.

Sequence in context: A355852 A290815 A355857 * A063335 A020264 A044177

Adjacent sequences: A354224 A354225 A354226 * A354228 A354229 A354230

Keyword

nonn

Author

Krishna Kumar Arumugam, May 20 2022

Status

approved