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Search: id:A063982
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| A063982 |
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Number of divisors of 2^n - 1 that are relatively prime to 2^m - 1 for all 0 < m < n. |
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+0
9
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| 1, 2, 2, 2, 2, 1, 2, 2, 2, 2, 4, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 2, 4, 2, 2, 4, 8, 2, 2, 2, 2, 2, 4, 4, 4, 2, 4, 2, 4, 2, 8, 4, 4, 2, 8, 4, 2, 4, 8, 8, 8, 2, 8, 2, 4, 4, 4, 4, 2, 2, 4, 4, 2, 4, 4, 8, 2, 4, 8, 4, 8, 4, 4, 8, 2, 2, 8, 2, 8, 4, 4, 4, 2, 2, 4, 4, 2, 2, 8, 16, 2, 4, 8, 4, 4, 2, 8, 8
(list; graph; listen)
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OFFSET
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1,2
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LINKS
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Sam Wagstaff, Cunningham Project, Factorizations of 2^n-1, n odd, n<1200
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EXAMPLE
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Divisors of 2^8-1 are {1, 3, 5, 15, 17, 51, 85, 255}, but only 1 and 17 are relatively prime to 2^m - 1 for all m < 8, thus a(8)=2.
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MATHEMATICA
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a = {1}; Do[ d = Divisors[2^n - 1]; l = Length[d]; c = 0; k = 1; While[ k < l + 1, If[ Union[ GCD[a, d[[k]] ]] == {1}, c++ ]; k++ ]; Print[c]; a = Union[ Flatten[ Append[a, Transpose[ FactorInteger[2^n - 1]][[ 1]] ]]], {n, 1, 100} ]
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CROSSREFS
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Cf. A064078.
Sequence in context: A037200 A090044 A036238 this_sequence A055020 A052435 A094701
Adjacent sequences: A063979 A063980 A063981 this_sequence A063983 A063984 A063985
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KEYWORD
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nonn,nice
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AUTHOR
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Vladeta Jovovic (vladeta(AT)eunet.rs), Sep 06 2001
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 10 2001
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