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A224540 Number of numbers k such that all terms of the Collatz (3x+1) iteration of k are <= 3^n. 2
1, 2, 4, 12, 36, 106, 249, 613, 1732, 8028, 23348, 69370, 210807, 634839, 1893582, 5686389, 17031777, 51073675, 153185957, 459516225, 1378707224, 4135278456 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..21.

EXAMPLE

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

MATHEMATICA

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

CROSSREFS

Cf. A006884, A006885, A095384, A224538.

Sequence in context: A192236 A149839 A149840 * A025579 A214936 A010552

Adjacent sequences:  A224537 A224538 A224539 * A224541 A224542 A224543

KEYWORD

nonn,more

AUTHOR

T. D. Noe, Apr 24 2013

EXTENSIONS

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

STATUS

approved

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Last modified May 19 22:32 EDT 2019. Contains 323411 sequences. (Running on oeis4.)