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A000477
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Related to the divisor function.
(Formerly M4973 N2135)
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0
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1, 15, 76, 275, 720, 1666, 3440, 6129, 11250, 17545, 28896, 41405, 65072, 85950, 128960, 162996, 238545, 286995, 404600, 482160, 662112, 756470, 1042560, 1150625, 1549730, 1732590, 2257920, 2443105, 3250800, 3421160, 4452096, 4791600, 6039522, 6296500, 8249580, 8349531, 10598960, 11150958, 13788000, 14002730, 17936352, 17796625, 22345312, 22965525, 27804240, 27842236, 35473920, 34300686, 42371875, 43150590, 51947896, 50941215, 63918720, 61474050, 75389440, 75550080, 89389890, 87320885, 109872000, 103239145, 125037632, 124877970, 147864576, 142433200, 175895280, 165370271, 200762520, 197524368, 230731200, 221249490, 274875120, 254353170, 304380722, 301408125, 351354080, 332308592
(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^2*sigma(k)*sigma(n-k),k=1..n-1)
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CROSSREFS
| Sequence in context: A051880 A007328 A049391 * A041430 A156941 A205440
Adjacent sequences: A000474 A000475 A000476 * A000478 A000479 A000480
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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 formula from Sean A. Irvine (sairvin(AT)xtra.co.nz), Nov 14 2010
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