id:A060872 - OEIS Search Results

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Sum of d*d' over all unordered pairs (d,d') with d*d' = n.

+0
4

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)

	OFFSET	`1,2`
	FORMULA	`a(n) = n * Ceiling( d(n)/2) where d is the number of divisors function.`
	EXAMPLE	`a(4)=8 because pairs of factors are 14 and 22 and 14 + 22 = 8.`
	MATHEMATICA	`Table[ n * Ceiling[ DivisorSigma[0, n] /2 ], {n, 1, 73} ]`
	CROSSREFS	`Cf. A060866.` `First differences of A083356.` `Sequence in context: A126102 A011433 A126139 this_sequence A162775 A066959 A086471` `Adjacent sequences: A060869 A060870 A060871 this_sequence A060873 A060874 A060875`
	KEYWORD	`nonn,easy`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com), May 04 2001`
	EXTENSIONS	`More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 23 2001`

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Last modified November 30 13:13 EST 2009. Contains 167758 sequences.

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