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A079788
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a(n) = count of numbers <= n for which the number of divisors is also <= tau(n).
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2
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1, 2, 3, 4, 4, 6, 5, 8, 7, 10, 6, 12, 7, 13, 14, 15, 8, 18, 9, 20, 17, 18, 10, 24, 13, 21, 22, 27, 11, 30, 12, 30, 25, 26, 27, 36, 13, 29, 30, 39, 14, 41, 15, 39, 40, 33, 16, 48, 20, 44, 36, 46, 17, 52, 38, 54, 39, 40, 18, 60, 19, 43, 54, 55, 44, 63, 20, 57, 46, 67, 21, 72, 22, 49
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OFFSET
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1,2
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LINKS
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Table of n, a(n) for n=1..74.
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EXAMPLE
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a(7) = 5 as 1, 2, 3, 5 and 7 qualify for the count.
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MATHEMATICA
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Do[s = 0; For[i = 1, i <= n, i++, If[DivisorSigma[0, i] <= DivisorSigma[0, n], s++ ]]; Print[s], {n, 1, 50}] - Ryan Propper (rpropper(AT)stanford.edu), Mar 30 2006
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PROG
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(PARI) for(n=1, 200, m=0; sn=sigma(n, 0); for(i = 1, n, if(sigma(i, 0)<=sn, m++)); print1(m", ")) - Herman Jamke (hermanjamke(AT)fastmail.fm), Apr 28 2007
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CROSSREFS
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Cf. A138009, A067004.
Sequence in context: A071324 A063655 A117248 * A146288 A199424 A184160
Adjacent sequences: A079785 A079786 A079787 * A079789 A079790 A079791
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Feb 03 2003
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EXTENSIONS
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More terms from Ryan Propper (rpropper(AT)stanford.edu), Mar 30 2006
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Apr 28 2007
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STATUS
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approved
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