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Search: id:A030231
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| A030231 |
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Number of distinct primes dividing n is even. |
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+0
5
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| 1, 6, 10, 12, 14, 15, 18, 20, 21, 22, 24, 26, 28, 33, 34, 35, 36, 38, 39, 40, 44, 45, 46, 48, 50, 51, 52, 54, 55, 56, 57, 58, 62, 63, 65, 68, 69, 72, 74, 75, 76, 77, 80, 82, 85, 86, 87, 88, 91, 92, 93, 94, 95, 96, 98, 99, 100, 104, 106, 108, 111, 112, 115, 116, 117, 118, 119
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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GCD[A008472(a[n]), A007947(a[n])]=1; see A014963. - Labos E. (labos(AT)ana.sote.hu), Mar 26 2003
Superset of A007774. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 23 2008]
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..1000
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FORMULA
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n such that sum(d|n, mu(d)*tau(d))=(-1)^omega(n)=+1 where mu(d)=A008683(d), tau(d)=A000005(d) and omega(d)=A001221(d). n such that A023900(n)>0 - Benoit Cloitre, Dec 08 2002
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PROGRAM
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(PARI) j=[]; for(n=1, 200, x=omega(n); if(Mod(x, 2)==0, j=concat(j, n))); j
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CROSSREFS
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Cf. A028260, A030230.
Sequence in context: A024619 A106543 A007774 this_sequence A056760 A084227 A100658
Adjacent sequences: A030228 A030229 A030230 this_sequence A030232 A030233 A030234
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KEYWORD
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nonn,easy,nice
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AUTHOR
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David W. Wilson (davidwwilson(AT)comcast.net)
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EXTENSIONS
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Corrected by Dan Pritikin (pritikd(AT)muohio.edu), May 29 2002
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