id:A054784 - OEIS Search Results

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Integers n such that Sigma[2n]-Sigma[n] is a power of 2, where Sigma is the sum of divisors of n.

+0
2

1, 2, 3, 4, 6, 7, 8, 12, 14, 16, 21, 24, 28, 31, 32, 42, 48, 56, 62, 64, 84, 93, 96, 112, 124, 127, 128, 168, 186, 192, 217, 224, 248, 254, 256, 336, 372, 381, 384, 434, 448, 496, 508, 512, 651, 672, 744, 762, 768, 868, 889, 896, 992, 1016, 1024, 1302, 1344, 1488 (list; graph; listen)

	OFFSET	`1,2`
	FORMULA	`A000203[2*a(n)]-A000203[a(n)]=2^w for some w.`
	EXAMPLE	`If n is a square-free product of Mersenne primes possibly multiplied by a power of 2, then Sigma[2n]-Sigma[n] is a power of 2.`
	CROSSREFS	`A000203, A000668.` `Sequence in context: A077436 A082752 A023758 this_sequence A018585 A018399 A029748` `Adjacent sequences: A054781 A054782 A054783 this_sequence A054785 A054786 A054787`
	KEYWORD	`nonn`
	AUTHOR	`Labos E. (labos(AT)ana.sote.hu), May 22 2000`

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Last modified August 19 23:53 EDT 2008. Contains 142930 sequences.

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