login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A072122 Numbers with 12 odd integers in their Collatz (or 3x+1) trajectory. 3
39, 78, 79, 153, 156, 157, 158, 305, 306, 307, 312, 314, 315, 316, 317, 610, 611, 612, 613, 614, 624, 628, 629, 630, 631, 632, 634, 647, 683, 687, 1220, 1221, 1222, 1224, 1226, 1228, 1229, 1241, 1248, 1256, 1257, 1258, 1260, 1261, 1262, 1264, 1265, 1268 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The Collatz (or 3x+1) function is f(x) = x/2 if x is even, 3x+1 if x is odd. The Collatz trajectory of n is obtained by applying f repeatedly to n until 1 is reached.

REFERENCES

J. Shallit and D. Wilson, The "3x+1" Problem and Finite Automata, Bulletin of the EATCS #46 (1992) pp. 182-185.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

J. Shallit and D. Wilson, The "3x+1" Problem and Finite Automata, Bulletin of the EATCS #46 (1992) pp. 182-185.

Index entries for 2-automatic sequences.

EXAMPLE

trajectory: 39, 118, 59, 178, 89, 268, 134, 67, 202, 101, 304, 152, 76, 38, 19, 58, 29, 88, 44, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1 has 12 odd numbers.

MATHEMATICA

odd12Q[n_]:=Count[NestWhileList[If[EvenQ[#], #/2, 3#+1]&, n, #>1&], _?OddQ]==12; Select[Range[1300], odd12Q] (* Harvey P. Dale, Oct 17 2011 *)

CROSSREFS

Cf. A062052-A062060.

Column k=12 of A354236.

Sequence in context: A253153 A044105 A044486 * A355852 A290815 A355857

Adjacent sequences: A072119 A072120 A072121 * A072123 A072124 A072125

KEYWORD

easy,nonn

AUTHOR

Jim Nastos, Jun 19 2002

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 3 15:16 EST 2022. Contains 358534 sequences. (Running on oeis4.)