A134666 - OEIS

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A134666

Number of multiply perfect numbers (A007691) having 2^n as the highest power of 2.

1, 1, 2, 2, 1, 4, 1, 5, 4, 4, 3, 6, 1, 3, 4, 5, 1, 9, 1, 19, 8, 9, 3, 5, 6, 7, 16, 13, 26, 20, 1, 6, 8, 6, 13, 23, 20, 6, 9, 33, 10, 11, 14, 18, 15, 13, 32, 23, 23, 18, 12, 20, 26, 21, 16, 17, 7, 11, 20, 15, 1, 10, 17, 14, 13, 26, 21, 16, 24, 13, 21, 27, 18, 14, 16, 21, 38, 19, 12, 26, 13, 23 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,3`
	COMMENTS	`It appears that a(n)>0 for all n. With the exception of n=2, a(n)=1 when n is p-1, where p is a Mersenne prime (A000043). Flammenkamp has an attactive graph of this sequence, including n for which there is incomplete data.`
	LINKS	`Achim Flammenkamp, The Multiply Perfect Numbers Page`
	EXAMPLE	`a(2)=2 because only 28 and 2178540 have 2^2 as their highest power of 2.`
	CROSSREFS	`Cf. A134665 (highest power of 2 for each MPN).` `Sequence in context: A018219 A174714 A116633 * A129712 A051720 A022693` `Adjacent sequences: A134663 A134664 A134665 * A134667 A134668 A134669`
	KEYWORD	`nonn`
	AUTHOR	`T. D. Noe (noe(AT)sspectra.com), Nov 05 2007`

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Last modified February 17 11:46 EST 2012. Contains 206011 sequences.