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A055515
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(2^n -1)/product(2^p -1) where the product is over all distinct primes p that divide n.
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0
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1, 1, 1, 5, 1, 3, 1, 85, 73, 11, 1, 195, 1, 43, 151, 21845, 1, 12483, 1, 11275, 2359, 683, 1, 798915, 1082401, 2731, 19173961, 704555, 1, 1649373, 1, 1431655765, 599479, 43691, 8727391, 3272356035, 1, 174763, 9588151, 11822705675, 1, 1649061309, 1
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OFFSET
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1,4
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LINKS
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FORMULA
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EXAMPLE
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a(12) = (2^12 -1)/((2^2 -1) (2^3 -1)) = 195.
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PROG
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(PARI) a(n) = my(f = factor(n)); (2^n-1)/prod(i=1, #f~, 2^f[i, 1] -1); \\ Michel Marcus, May 18 2014
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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