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A090748
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Numbers n such that 2^(n+1) - 1 is prime.
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31
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1, 2, 4, 6, 12, 16, 18, 30, 60, 88, 106, 126, 520, 606, 1278, 2202, 2280, 3216, 4252, 4422, 9688, 9940, 11212, 19936, 21700, 23208, 44496, 86242, 110502, 132048, 216090, 756838, 859432, 1257786, 1398268, 2976220, 3021376, 6972592, 13466916, 20996010, 24036582, 25964950, 30402456, 32582656
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OFFSET
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1,2
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COMMENTS
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Number of proper divisors of n-th even perfect number that are multiples of n-th Mersenne prime A000668(n). - Omar E. Pol, Feb 28 2008
Base 2 logarithm of n-th even superperfect number A061652(n). Also base 2 logarithm of n-th superperfect number A019279(n), assuming there are no odd superperfect numbers. - Omar E. Pol, Apr 11 2008
Number of 0's in binary expansion of n-th even perfect number (see A135650). - Omar E. Pol, May 04 2008
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LINKS
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FORMULA
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EXAMPLE
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1 is in the sequence because 2^2 - 1 = 3 is prime.
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MATHEMATICA
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PROG
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Feb 03 2004
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EXTENSIONS
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STATUS
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approved
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