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A037143
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Numbers with at most 2 prime factors (counted with multiplicity).
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17
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1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 13, 14, 15, 17, 19, 21, 22, 23, 25, 26, 29, 31, 33, 34, 35, 37, 38, 39, 41, 43, 46, 47, 49, 51, 53, 55, 57, 58, 59, 61, 62, 65, 67, 69, 71, 73, 74, 77, 79, 82, 83, 85, 86, 87, 89, 91, 93, 94, 95, 97, 101, 103, 106, 107, 109, 111, 113, 115, 118
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| A001222(a(n)) <= 2; A054576(a(n)) = 1. - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Mar 10 2006
Products of two non-composite numbers. [From Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Apr 15 2010]
Also numbers such that exist permutations of all divisors only with coprime adjacent elements: A109810(a(n))>0. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), May 24 2010]
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LINKS
| R. Zumkeller, Table of n, a(n) for n = 1..1000
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CROSSREFS
| Union of A008578 and A001358. Complement of A033942. Cf. A063928.
A101040(a(n))=1 for n>1.
A139690 is a subsequence.
Subsequence of A037144. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), May 24 2010]
Sequence in context: A166155 A063538 A167207 * A048627 A152757 A062462
Adjacent sequences: A037140 A037141 A037142 * A037144 A037145 A037146
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Henry Bottomley (se16(AT)btinternet.com), Aug 15 2001
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