id:A123926 - OEIS Search Results

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Greatest common divisor of sigma_k(n) for all k >= 1.

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1, 1, 2, 1, 2, 2, 2, 1, 1, 2, 2, 2, 2, 2, 4, 1, 2, 1, 2, 6, 4, 2, 2, 2, 1, 2, 4, 2, 2, 4, 2, 3, 4, 2, 4, 1, 2, 2, 4, 2, 2, 4, 2, 6, 2, 2, 2, 2, 3, 3, 4, 2, 2, 4, 4, 2, 4, 2, 2, 12, 2, 2, 2, 1, 4, 4, 2, 6, 4, 4, 2, 1, 2, 2, 2, 2, 4, 4, 2, 2, 1, 2, 2, 4, 4, 2, 4, 2, 2, 2, 4, 6, 4, 2, 4, 6, 2, 3, 2, 1, 2, 4, 2, 2, 8 (list; graph; listen)

	OFFSET	`1,3`
	COMMENT	`Has the property that if gcd(n,m) = 1, then a(n)a(m) divides a(nm). First inequality is a(4) = 1, a(5) = 2, but a(20) = 6. It appears that a(n) also always divides sigma_0(n) = tau(n).`
	EXAMPLE	`For n=4, sigma_1(n) = 7, sigma_2(n) = 21, both divisible by 7, but sigma_3(n) = 73, which is not, so a(4) = 1.`
	CROSSREFS	`Cf. A109974, A000005, A000203, A001157.` `Sequence in context: A082070 A082071 A082902 this_sequence A082064 A082065 A082055` `Adjacent sequences: A123923 A123924 A123925 this_sequence A123927 A123928 A123929`
	KEYWORD	`nice,nonn`
	AUTHOR	`Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), Nov 21 2006`

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Last modified December 17 23:40 EST 2009. Contains 171025 sequences.

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