id:A080225 - OEIS Search Results

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Number of perfect divisors of n.

+0
7

0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0 (list; graph; listen)

	OFFSET	`1,84`
	COMMENT	`Number of divisors d of n with sigma(d)=2*d (sigma=A000203); A080224(n)+a(n)+A080226(n)=A000005(n).`
	LINKS	`Eric Weisstein's World of Mathematics, Perfect Number.`
	EXAMPLE	`Divisors of n=84: {1,2,3,4,6,7,12,14,21,24,28,42}, two of them are perfect: 6=A000396(1) and 28=A000396(2), therefore a(84)=2.`
	CROSSREFS	`Cf. A000396, A000203.` `Sequence in context: A028605 A070205 A138363 this_sequence A122841 A060862 A066087` `Adjacent sequences: A080222 A080223 A080224 this_sequence A080226 A080227 A080228`
	KEYWORD	`nonn`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 07 2003`

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Last modified November 25 14:49 EST 2009. Contains 167514 sequences.

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