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A078417 Numbers n such that h(n) = h(n+1), where h(n) is the length of n, f(n), f(f(n)), ..., 1 in the Collatz (or 3x + 1) problem. (The earliest "1" is meant.) 3
12, 14, 18, 20, 22, 28, 29, 34, 36, 37, 44, 45, 49, 50, 52, 54, 60, 62, 65, 66, 68, 69, 76, 78, 82, 84, 86, 92, 94, 98, 99, 100, 101, 108, 109, 114, 116, 118, 124, 125, 130, 131, 132, 133, 140, 142, 145, 146, 148, 150, 156, 157, 162, 164, 165, 172, 173, 177, 178 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Recall that f(n) = n/2 if n is even; = 3n + 1 if n is odd.

LINKS

Eric M. Schmidt, Table of n, a(n) for n = 1..10000

Marcus Elia, Amanda Tucker, Consecutive Integers and the Collatz Conjecture, arXiv:1511.09141 [math.NT], 2015.

Lynn E. Garner, On heights in the Collatz 3n+1 problem, Discrete Math, 55 (1985), 57-64.

Eric Weisstein's World of Mathematics, Collatz Problem

Wikipedia, Collatz Conjecture

Index entries for sequences related to 3x+1 (or Collatz) problem

EXAMPLE

n, f(n), f(f(n)), ..., 1 for n = 12, 13, respectively are: 12, 6, 3, 10, 5, 16, 8, 4, 2, 1; 13, 40, 20, 10, 5, 16, 8, 4, 2, 1, which are both of length 10. Hence h(12) = h(13) = 10 and 12 belongs to the sequence.

CROSSREFS

Cf. A006577.

Sequence in context: A208156 A135770 A091989 * A107835 A257966 A255842

Adjacent sequences:  A078414 A078415 A078416 * A078418 A078419 A078420

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Dec 29 2002

STATUS

approved

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Last modified January 25 23:08 EST 2020. Contains 331270 sequences. (Running on oeis4.)