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Search: id:A000379
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| A000379 |
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A 2-way classification of integers: complement of A000028.
(Formerly M4065 N1685)
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+0
14
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| 1, 6, 8, 10, 12, 14, 15, 18, 20, 21, 22, 26, 27, 28, 32, 33, 34, 35, 36, 38, 39, 44, 45, 46, 48, 50, 51, 52, 55, 57, 58, 62, 63, 64, 65, 68, 69, 74, 75, 76, 77, 80, 82, 85, 86, 87, 91, 92, 93, 94, 95, 98, 99, 100, 106, 111, 112, 115, 116, 117, 118, 119, 120, 122, 123, 124, 125, 129
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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This sequence and A000028 (its complement) give the unique solution to the problem of splitting the positive integers into two classes in such a way that products of pairs of distinct elements from either class occur with the same multiplicities [Lambek and Moser]. Cf. A000069, A001969.
See A000028 for precise definition, Maple program, etc.
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REFERENCES
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J. Lambek and L. Moser, On some two way classifications of integers, Canad. Math. Bull. 2 (1959), 85-89.
J. Roberts, Lure of the Integers, Math. Assoc. America, 1992, p. 22.
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LINKS
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N. J. A. Sloane, Table of n, a(n) for n=1..10000
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CROSSREFS
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Cf. A133008, A000028 (complement), A000201, A001950. Different from A123240 (e.g. does not contain 180).
Adjacent sequences: A000376 A000377 A000378 this_sequence A000380 A000381 A000382
Sequence in context: A123240 A131181 A064176 this_sequence A065985 A060652 A020739
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KEYWORD
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nonn,easy,nice
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AUTHOR
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njas
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EXTENSIONS
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Edited by njas, Dec 20 2007, to restore the original definition.
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