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Search: id:A128487
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| A128487 |
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Irregular array where n-th row is the positive integers < n which are coprime to exactly one distinct prime divisor of n. |
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+0
3
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| 1, 1, 2, 1, 3, 1, 2, 3, 4, 2, 3, 4, 1, 2, 3, 4, 5, 6, 1, 3, 5, 7, 1, 2, 4, 5, 7, 8, 2, 4, 5, 6, 8, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 2, 3, 4, 8, 9, 10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 2, 4, 6, 7, 8, 10, 12, 3, 5, 6, 9, 10, 12, 1, 3, 5, 7, 9, 11, 13, 15, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14
(list; graph; listen)
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OFFSET
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2,3
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COMMENT
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Number of terms in n-th row is A126080(n). Row 1 has zero terms, so the first listed row is row 2.
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EXAMPLE
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Concerning row 12: 1,5,7,11 don't appear because they are each coprime to 2 AND 3 (the distinct prime divisors of 12). 6 doesn't appear because it is coprime to neither prime dividing 12. The row consists of 2,3,4,8,9,10 because each term is coprime to exactly one prime divisor of 12 (ie, is coprime to 2 or 3, but not to both).
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CROSSREFS
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Cf. A126080, A128488.
Adjacent sequences: A128484 A128485 A128486 this_sequence A128488 A128489 A128490
Sequence in context: A038566 A020652 A096107 this_sequence A056609 A014673 A085392
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KEYWORD
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nonn,tabf
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), Mar 04 2007
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 08 2007
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