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A175906
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Numbers n of the form 2^(A000043-1)*A046528 such that sigma(n) is perfect number.
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0
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OFFSET
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1,1
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COMMENTS
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sigma(sigma(A046528(2,12,13,18,21,22,56,57,175,176,177,..))) is Mersenne prime.
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LINKS
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Table of n, a(n) for n=1..9.
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FORMULA
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a(n)= 2^( A000043(2,5,5,6,7,7,8,8,9,9,9,..)-1)*A046528(2,12,13,18,21,22,56,57,175,176,177,..).
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EXAMPLE
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45091651584=2^18*3*7*8191, sigma(45091651584)=137438691328 is perfect number.
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CROSSREFS
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Cf. A000396, A000203, A000668, A000043, A046528, A063103.
Sequence in context: A013862 A116233 A145745 * A144546 A165970 A081357
Adjacent sequences: A175903 A175904 A175905 * A175907 A175908 A175909
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KEYWORD
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nonn
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AUTHOR
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Manuel Valdivia, Oct 12 2010
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STATUS
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approved
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