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

Author

Krishna Kumar Arumugam, May 20 2022

Keywords

• nonn

Examples

			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.
		

Crossrefs

Cf. A005408, A072122.

Programs

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 *)

Formula

{ A005408 } intersect { A072122 }.