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A090178
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a(1) = 2; for n > 1, a(n) = n + prime(n-1).
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6
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2, 4, 6, 9, 12, 17, 20, 25, 28, 33, 40, 43, 50, 55, 58, 63, 70, 77, 80, 87, 92, 95, 102, 107, 114, 123, 128, 131, 136, 139, 144, 159, 164, 171, 174, 185, 188, 195, 202, 207, 214, 221, 224, 235, 238, 243, 246, 259, 272, 277, 280, 285, 292, 295, 306, 313, 320, 327
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OFFSET
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1,1
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COMMENTS
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Sum of index n and the corresponding n-th term of noncomposite numbers (A008578).
Does n > 2 exist such that n*prime(n-1)/(n+prime(n-1)), i.e., A164931(n)/a(n) is an integer? - Jaroslav Krizek, Aug 31 2009
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REFERENCES
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M. Feenstra, P. J. Carter and C. P. Harding, The Ultimate I.Q. Book, Wardlock, see p. 99.
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LINKS
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FORMULA
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EXAMPLE
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a(2) = 2 + prime(1) = 4; a(5) = 5 + prime(4) = 12; a(9) = 9 + prime(8) = 28.
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MATHEMATICA
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PROG
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(Magma) [n + NthPrime(n-1): n in [1..58] ]; // Klaus Brockhaus, Sep 09 2009
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CROSSREFS
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The published version (A048171) is said to be incorrect.
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KEYWORD
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nonn
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AUTHOR
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Pab Ter (pabrlos(AT)yahoo.com), May 29 2004
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EXTENSIONS
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Definition corrected, second comment and example edited by Klaus Brockhaus, Sep 09 2009
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STATUS
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approved
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