id:A099777 - OEIS Search Results

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Number of divisors of 2n.

+0
2

2, 3, 4, 4, 4, 6, 4, 5, 6, 6, 4, 8, 4, 6, 8, 6, 4, 9, 4, 8, 8, 6, 4, 10, 6, 6, 8, 8, 4, 12, 4, 7, 8, 6, 8, 12, 4, 6, 8, 10, 4, 12, 4, 8, 12, 6, 4, 12, 6, 9, 8, 8, 4, 12, 8, 10, 8, 6, 4, 16, 4, 6, 12, 8, 8, 12, 4, 8, 8, 12, 4, 15, 4, 6, 12, 8, 8, 12, 4, 12, 10, 6, 4, 16, 8, 6, 8, 10, 4, 18, 8, 8, 8, 6, 8 (list; graph; listen)

	OFFSET	`1,1`
	FORMULA	`Moebius transform is period 2 sequence [2, 1, ...]. - Michael Somos Sep 20 2005` `G.f.: Sum_{k>0} x^k(2+x^k)/(1-x^(2k)) = Sum_{k>0} 2*x^(2k-1)/(1-x^(2k-1))+x^(2k)/(1-x^(2k)) . - Michael Somos Sep 20 2005`
	EXAMPLE	`Example: a(7)=4 because the divisors of 14 are: 1,2,7 and 14.`
	MAPLE	`with(numtheory): seq(tau(2*n), n=1..100);`
	PROGRAM	`(PARI) a(n)=if(n<1, 0, numdiv(2n)) / Michael Somos Sep 20 2005 */`
	CROSSREFS	`Bisection of A000005.` `Cf. A000005, A099774.` `Sequence in context: A120508 A029085 A087875 this_sequence A131798 A114212 A108355` `Adjacent sequences: A099774 A099775 A099776 this_sequence A099778 A099779 A099780`
	KEYWORD	`nonn,easy`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com), Nov 19 2004`
	EXTENSIONS	`More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 03 2004`

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Last modified December 15 00:47 EST 2009. Contains 170825 sequences.

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