A080224 - OEIS

This site is supported by donations to The OEIS Foundation.

A080224

Number of abundant divisors of n.

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 2, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 3, 0, 0, 0, 2, 0, 1, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 2, 0, 1, 0, 0, 0, 4, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 5, 0, 0, 0, 0, 0, 1, 0, 3, 0, 0, 0, 3, 0, 0, 0, 1, 0, 3, 0, 0, 0, 0, 0, 4, 0, 0, 0, 2, 0, 1, 0, 1, 0 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,24`
	COMMENTS	`Number of divisors d of n with sigma(d)>2*d (sigma=A000203); a(n)+A080225(n)+A080226(n)=A000005(n).` `a(n)>0 iff n is abundant: a(A005101(n))>0, a(A000396(n))=0 and a(A005100(n))=0; a(A091191(n))=1; a(A091192(n))>1; a(A091193(n))=n and a(m)<>n for m < A091193(n). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Dec 27 2003`
	LINKS	`R. Zumkeller, Table of n, a(n) for n = 1..10000` `Eric Weisstein's World of Mathematics, Abundant Number.`
	EXAMPLE	`Divisors of n=24: {1,2,3,4,6,8,12,24}, two of them are abundant: 12=A005101(1) and 24=A005101(4), therefore a(24)=2.`
	CROSSREFS	`Cf. A005101, A000203.` `Sequence in context: A122841 A060862 A066087 * A010105 A083916 A083893` `Adjacent sequences: A080221 A080222 A080223 * A080225 A080226 A080227`
	KEYWORD	`nonn`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 07 2003`

Content is available under The OEIS End-User License Agreement .

Last modified February 16 21:14 EST 2012. Contains 205971 sequences.