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A078417
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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.)
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0
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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; internal format)
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OFFSET
| 1,1
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COMMENTS
| Recall that f(n) = n/2 if n is even; = 3n + 1 if n is odd.
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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.
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CROSSREFS
| Sequence in context: A159251 A135770 A091989 * A107835 A101557 A019292
Adjacent sequences: A078414 A078415 A078416 * A078418 A078419 A078420
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KEYWORD
| nonn
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AUTHOR
| Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Dec 29 2002
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