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A224538 Number of numbers k such that all terms of the Collatz (3x+1) iteration of k are <= 10^n. 3
1, 4, 49, 340, 4235, 39706, 397068, 3970918, 39523168, 395436300, 3953296865 (list; graph; refs; listen; history; text; internal format)
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

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Last modified May 24 11:23 EDT 2019. Contains 323529 sequences. (Running on oeis4.)