A224540 Number of numbers k such that all terms of the Collatz (3x+1) iteration of k are <= 3^n.

1, 2, 4, 12, 36, 106, 249, 613, 1732, 8028, 23348, 69370, 210807, 634839, 1893582, 5686389, 17031777, 51073675, 153185957, 459516225, 1378707224, 4135278456

Offset: 0

Author

T. D. Noe, Apr 24 2013

Keywords

• nonn
• more

Examples

			For n = 3, the twelve k are 1, 2, 3, 4, 5, 6, 8, 10, 12, 16, 20, and 24.
		

Crossrefs

Cf. A006884, A006885, A095384, A224538.

Programs

Mathematica

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; Table[Select[Range[3^n], Max[Collatz[#]] <= 3^n &], {n, 8}]

Extensions

a(20)-a(21) from Donovan Johnson, Jun 05 2013