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A113981 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. +0
2
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; listen)
OFFSET

1,2

COMMENT

Sequence is a permutation of the positive integers.

LINKS

Diana Mecum, Table of n, a(n) for n = 1..1195 [From Diana Mecum (diana.mecum(AT)gmail.com), Aug 15 2008]

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.

CROSSREFS

Cf. A113982.

Sequence in context: A073846 A110458 A114112 this_sequence A143692 A114792 A113324

Adjacent sequences: A113978 A113979 A113980 this_sequence A113982 A113983 A113984

KEYWORD

nonn

AUTHOR

Leroy Quet (qq-quet(AT)mindspring.com), Nov 11 2005

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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Last modified November 18 20:14 EST 2008. Contains 147244 sequences.


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