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Search: id:A060872
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| A060872 |
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Sum of d*d' over all unordered pairs (d,d') with d*d' = n. |
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+0
4
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| 1, 2, 3, 8, 5, 12, 7, 16, 18, 20, 11, 36, 13, 28, 30, 48, 17, 54, 19, 60, 42, 44, 23, 96, 50, 52, 54, 84, 29, 120, 31, 96, 66, 68, 70, 180, 37, 76, 78, 160, 41, 168, 43, 132, 135, 92, 47, 240, 98, 150, 102, 156, 53, 216, 110, 224, 114, 116, 59, 360, 61, 124, 189, 256
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(n) = n * Ceiling( d(n)/2) where d is the number of divisors function.
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EXAMPLE
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a(4)=8 because pairs of factors are 1*4 and 2*2, and 1*4 + 2*2 = 8.
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MATHEMATICA
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Table[ n * Ceiling[ DivisorSigma[0, n] /2 ], {n, 1, 73} ]
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CROSSREFS
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Cf. A060866.
First differences of A083356.
Sequence in context: A126102 A011433 A126139 this_sequence A066959 A086471 A097505
Adjacent sequences: A060869 A060870 A060871 this_sequence A060873 A060874 A060875
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KEYWORD
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nonn,easy
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AUTHOR
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njas, May 04 2001
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 23 2001
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