A158276 - OEIS

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A158276

Numbers k such that sigma_1(k) not divides sigma_2(k).

2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 17, 18, 19, 21, 22, 23, 24, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,1`
	COMMENTS	`a(n) is numbers k such that antiharmonic mean of divisors of k is not an integer. Antiharmonic mean of divisors of number m = Product (p_i^e_i) is A001157(m)/A000203(m) = Product ((p_i^(e_i+1)+1)/(p_i+1)). a(n) = k = A001157(k)/A000203(k) for A001157(k)/A000203(k)is not integer. a(n)non-occurring in A020487.`
	EXAMPLE	`a(12) = 15, sigma_2(15)/sigma_1(15)=260/24 = 65/6 (not integer).`
	CROSSREFS	`Cf. A001157, A000203, A020487.` `Sequence in context: A028797 A028773 A028813 * A028793 A028753 A028745` `Adjacent sequences: A158273 A158274 A158275 * A158277 A158278 A158279`
	KEYWORD	`nonn`
	AUTHOR	`Jaroslav Krizek (jaroslav.krizek(AT)atlas.cz), Mar 15 2009`

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Last modified February 15 05:38 EST 2012. Contains 205694 sequences.