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A113981
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a(1)=1. a(n) is smallest positive integer that does not occur earlier in the sequence and is such that d(a(n)) does not equal d(a(n-1)), where d(n) is the number of positive divisors of n.
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2
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1, 2, 4, 3, 6, 5, 8, 7, 10, 9, 12, 11, 14, 13, 16, 15, 18, 17, 20, 19, 23, 24, 21, 22, 26, 25, 28, 27, 30, 29, 32, 31, 36, 37, 40, 33, 34, 41, 42, 35, 38, 39, 44, 43, 46, 45, 48, 47, 50, 49, 52, 51, 54, 53, 56, 55, 59, 60, 57, 58, 62, 61, 64, 63, 66, 65, 68, 67, 70, 69, 72, 71
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Sequence is a permutation of the positive integers.
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LINKS
| Diana Mecum, Table of n, a(n) for n = 1..1195 [From Diana Mecum (diana.mecum(AT)gmail.com), Aug 15 2008]
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EXAMPLE
| Since d(a(4)) = d(3) = 2, d(a(5)) cannot be 2. a(5)= 6 is the smallest positive integer not occurring earlier in the sequence where d(a(5)) is not 2, since d(6) = 4.
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CROSSREFS
| Cf. A113982.
Sequence in context: A073846 A110458 A114112 * A143692 A114792 A113324
Adjacent sequences: A113978 A113979 A113980 * A113982 A113983 A113984
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Nov 11 2005
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EXTENSIONS
| More terms from Diana Mecum (diana.mecum(AT)gmail.com), May 29 2007
More terms from Diana Mecum (diana.mecum(AT)gmail.com), Aug 15 2008
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