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A054784 Integers n such that Sigma[2n]-Sigma[n] is a power of 2, where Sigma is the sum of divisors of n. 1
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; refs; listen; history; internal format)
OFFSET

1,2

FORMULA

A000203[2*a(n)]-A000203[a(n)]=2^w for some w.

EXAMPLE

If n is a squarefree 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 * A018585 A018399 A029748

Adjacent sequences:  A054781 A054782 A054783 * A054785 A054786 A054787

KEYWORD

nonn

AUTHOR

Labos E. (labos(AT)ana.sote.hu), May 22 2000

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Last modified February 17 04:56 EST 2012. Contains 205985 sequences.