id:A051281 - OEIS Search Results

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Sum of divisors of n, sigma(n) (A000203), is a power of number of divisors of n, d(n) (A000005).

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1, 3, 7, 31, 127, 217, 889, 2667, 3937, 8191, 27559, 57337, 131071, 172011, 253921, 524287, 917497, 1040257, 1777447, 3670009, 4063201, 11010027, 12189603, 16252897, 16646017, 66584449, 113770279, 116522119, 225735769 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`All Mersenne primes (A000668) are terms.`
	EXAMPLE	`d(217)=4; sigma(217)=256=4^4.`
	CROSSREFS	`Sequence in context: A003260 A152058 A138865 this_sequence A145038 A138864 A105768` `Adjacent sequences: A051278 A051279 A051280 this_sequence A051282 A051283 A051284`
	KEYWORD	`nonn,nice`
	AUTHOR	`Michel ten Voorde (seqfan(AT)tenvoorde.org)`
	EXTENSIONS	`More terms from Jud McCranie (j.mccranie(AT)comcast.net)`

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Last modified November 25 08:46 EST 2009. Contains 167481 sequences.

AT&T Labs Research