A224538 Number of numbers k such that all terms of the Collatz (3x+1) iteration of k are <= 10^n.

1, 4, 49, 340, 4235, 39706, 397068, 3970918, 39523168, 395436300, 3953296865

Offset

0,2

Links

Table of n, a(n) for n=0..10.

Example

For n = 1, the four k are 1, 2, 4, and 8.

Mathematica

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; Table[Length[Select[Range[10^n], Max[Collatz[#]] <= 10^n &]], {n, 0, 5}]

Crossrefs

Cf. A006884, A006885, A095384, A222291, A224540.

Sequence in context: A000596 A113525 A290263 * A064751 A045787 A067474

Adjacent sequences: A224535 A224536 A224537 * A224539 A224540 A224541

Keyword

nonn,more

Author

T. D. Noe, Apr 24 2013

Extensions

a(10) from Donovan Johnson, Jun 05 2013

Status

approved