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A330710 Numbers that reach 1 in the 3x + 5 variation of Collatz map. 0
1, 2, 4, 8, 9, 16, 18, 32, 36, 41, 53, 64, 69, 72, 82, 106, 107, 111, 128, 138, 141, 143, 144, 163, 164, 169, 189, 212, 214, 217, 219, 222, 231, 247, 256, 263, 276, 281, 282, 286, 287, 288, 299, 326, 328, 331, 338, 349, 363, 373, 378, 381, 383, 397 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

In this variation of the Collatz function, f(x) = x/2 if x is even, 3x + 5 if x is odd.

f(a(n)) will end in the loop 8, 4, 2, 1.

For any odd number n in the sequence, n*2^x where x is a positive integer will also be in the sequence.

LINKS

Table of n, a(n) for n=1..54.

EXAMPLE

For n = 53, the numbers produced are 53 -> 164 -> 82 -> 41 -> 128 -> 64 -> 32 -> 16 -> 8 -> 4 -> 2 -> 1 -> 8 -> 4 -> 2 -> 1 -> ...

MATHEMATICA

Select[Range@ 400, Function[n, NestWhile[If[EvenQ@ #, #/2, 3 # + 5] &, n, And[FreeQ[{##}, 1], Count[{##}, n] <= 2] &, All, 120] == 1]] (* Michael De Vlieger, Dec 27 2019 *)

CROSSREFS

Cf. A000079, A181762.

Sequence in context: A175338 A071601 A114400 * A023898 A125853 A080025

Adjacent sequences:  A330706 A330707 A330708 * A330711 A330712 A330713

KEYWORD

nonn

AUTHOR

Cara Bennett, Dec 27 2019

STATUS

approved

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Last modified July 5 20:01 EDT 2020. Contains 335473 sequences. (Running on oeis4.)