id:A124315 - OEIS Search Results

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a(n) = Sum_{ d divides n } sigma_0(lcm(d,n/d)), where sigma is the number of divisors function.

+0
2

1, 2, 2, 4, 2, 4, 2, 6, 4, 4, 2, 8, 2, 4, 4, 9, 2, 8, 2, 8, 4, 4, 2, 12, 4, 4, 6, 8, 2, 8, 2, 12, 4, 4, 4, 16, 2, 4, 4, 12, 2, 8, 2, 8, 8, 4, 2, 18, 4, 8, 4, 8, 2, 12, 4, 12, 4, 4, 2, 16, 2, 4, 8, 16, 4, 8, 2, 8, 4, 8, 2, 24, 2, 4, 8, 8, 4, 8, 2, 18, 9, 4, 2, 16, 4, 4, 4, 12, 2, 16, 4, 8, 4, 4, 4, 24, 2, 8 (list; graph; listen)

	OFFSET	`1,2`
	FORMULA	`a(p)=2 iff p is a prime.`
	MATHEMATICA	`Table[Plus @@ Map[DivisorSigma[0, GCD[ #, n/# ]] &, Divisors@n], {n, 98}]`
	CROSSREFS	`Cf. A001616, A061884, A124316.` `Sequence in context: A118776 A092520 A129089 this_sequence A101113 A055155 A085191` `Adjacent sequences: A124312 A124313 A124314 this_sequence A124316 A124317 A124318`
	KEYWORD	`mult,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 30 2006`

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Last modified August 19 23:53 EDT 2008. Contains 142930 sequences.

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