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A217468
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Composite values of n such that 2^n == 2 (mod n*(n-1)).
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7
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OFFSET
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1,1
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COMMENTS
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No other terms below 2^64.
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LINKS
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EXAMPLE
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a(1) = 91625794219 = (2^38 - 2^19 + 1)/3 = A019320(114).
a(2) = 8796093022207 = 2^43 - 1 = A019320(43).
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PROG
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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STATUS
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approved
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