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Search: id:A002472
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| A002472 |
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Number of pairs x,y such that y-x=2, (x,n)=1, (y,n)=1 and 1 <= x <= n.
(Formerly M0411 N0157)
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+0
1
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| 1, 1, 1, 2, 3, 1, 5, 4, 3, 3, 9, 2, 11, 5, 3, 8, 15, 3, 17, 6, 5, 9, 21, 4, 15, 11, 9, 10, 27, 3, 29, 16, 9, 15, 15, 6, 35, 17, 11, 12, 39, 5, 41, 18, 9, 21, 45, 8, 35, 15, 15, 22, 51, 9, 27, 20, 17, 27, 57, 6, 59, 29, 15, 32, 33, 9, 65, 30, 21, 15, 69, 12, 71, 35, 15, 34, 45, 11, 77, 24, 27
(list; graph; listen)
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OFFSET
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1,4
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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).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
Golubev, V. A.; Nombres de Mersenne et caracteres du nombre 2. Mathesis 67 1958 257-262.
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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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Multiplicative with a(p^e) = p^(e-1) if p = 2; (p-2)*p^(e-1) if p > 2. - David W. Wilson (davidwwilson(AT)comcast.net), Aug 01, 2001.
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CROSSREFS
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Adjacent sequences: A002469 A002470 A002471 this_sequence A002473 A002474 A002475
Sequence in context: A047706 A114711 A166285 this_sequence A060116 A114690 A049274
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KEYWORD
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nonn,nice,easy,mult
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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More terms from David W. Wilson (davidwwilson(AT)comcast.net)
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