A125721 - OEIS

This site is supported by donations to The OEIS Foundation.

A125721

a(n)=2*n!/d(n!); d(m)=A000005(m) is the number of divisors of m.

2, 2, 2, 3, 6, 15, 48, 168, 840, 4536, 26880, 147840, 1209600 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,1`
	COMMENTS	`a(3)=3 and a(5)=15 are the only odd numbers in this sequence.`
	REFERENCES	`P. Erdos, solved by J. Fiedler, Elem. Math. 16 (1961), 42-44, Aufgabe 374.`
	FORMULA	`a(n)=2*A000142(n)/A027423(n).`
	EXAMPLE	`a(4)=24!/d(4!)=224/8=6.`
	CROSSREFS	`Cf. A000142, A027423.` `Sequence in context: A147851 A143596 A091712 * A049798 A165198 A024682` `Adjacent sequences: A125718 A125719 A125720 * A125722 A125723 A125724`
	KEYWORD	`nonn`
	AUTHOR	`Franz Vrabec (franz.vrabec(AT)aon.at), Feb 01 2007`

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

Last modified February 17 02:31 EST 2012. Contains 205978 sequences.