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Search: id:A007438
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| A007438 |
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Moebius transform of triangular numbers.
(Formerly M1339)
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+0
4
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| 1, 2, 5, 7, 14, 13, 27, 26, 39, 38, 65, 50, 90, 75, 100, 100, 152, 111, 189, 148, 198, 185, 275, 196, 310, 258, 333, 294, 434, 292, 495, 392, 490, 440, 588, 438, 702, 549, 684, 584, 860
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(n)=|{(x,y):1<=x<=y<=n, gcd(x,y,n)=1}|. E.g. a(4)=7 because of the pairs (1,1), (1,2), (1,3), (1,4), (2,3), (3,3), (3,4) - Steve Butler (sbutler(AT)math.ucsd.edu), Apr 18 2006
Partial sums of a(n) give A015631(n) - Steve Butler (sbutler(AT)math.ucsd.edu), Apr 18 2006
Equals row sums of triangle A159904. [From Gary W. Adamson (qntmpkt(AT)yahoo.com), Apr 25 2009]
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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N. J. A. Sloane, Transforms
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CROSSREFS
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A159904 [From Gary W. Adamson (qntmpkt(AT)yahoo.com), Apr 25 2009]
Sequence in context: A023242 A164570 A126338 this_sequence A031457 A044990 A133146
Adjacent sequences: A007435 A007436 A007437 this_sequence A007439 A007440 A007441
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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