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A000441
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Related to the divisor function.
(Formerly M4613 N1968)
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0
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1, 9, 34, 95, 210, 406, 740, 1161, 1920, 2695, 4116, 5369, 7868, 9690, 13640, 16116, 22419, 25365, 34160, 38640, 50622, 55154, 73320, 77225, 100100, 107730, 135576, 141085, 182340, 184760, 233616, 243408, 297738, 301420, 385110, 377511, 467210, 478842, 578400, 571130, 716352, 691999, 850828, 854865, 1011540, 990196, 1239504, 1170414, 1418725, 1415250, 1672216, 1606059, 1982340, 1868790, 2254000, 2216160, 2576940, 2472395, 3068520, 2827045, 3371312, 3314934, 3864864, 3661840, 4458960, 4122041, 4936596, 4783632, 5512920, 5203590, 6390540, 5817954, 6872528, 6717075, 7727300, 7208432, 8745828
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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REFERENCES
| N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
J. Touchard, On prime numbers and perfect numbers, Scripta Math., 129 (1953), 35-39.
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FORMULA
| a(n)=sum(k*sigma(k)*sigma(n-k),k=1..n-1)
Convolution of A000203 with A064987
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CROSSREFS
| Sequence in context: A106598 A014816 A147691 * A067989 A005344 A050478
Adjacent sequences: A000438 A000439 A000440 * A000442 A000443 A000444
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms and formulas from Sean A. Irvine (sairvin(AT)xtra.co.nz), Nov 14 2010
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