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A053287
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Euler totient function (A000010) of 2^n - 1.
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21
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1, 2, 6, 8, 30, 36, 126, 128, 432, 600, 1936, 1728, 8190, 10584, 27000, 32768, 131070, 139968, 524286, 480000, 1778112, 2640704, 8210080, 6635520, 32400000, 44717400, 113467392, 132765696, 533826432, 534600000, 2147483646, 2147483648, 6963536448, 11452896600
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OFFSET
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1,2
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COMMENTS
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Number of elements of multiplicative order 2^n - 1 in GF(2^n).
n divides a(n) because 2^a(n) mod 2^n - 1 is 1, 2^n mod 2^n - 1 is 1, so n | a(n). A011260(n) = a(n)/n. - Jinyuan Wang, Oct 31 2018
The set {a(n)/(2^n-1)} is dense in [0, 1] (Luca, 2003). - Amiram Eldar, Mar 04 2021
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LINKS
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FORMULA
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MAPLE
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a := n -> numtheory:-phi(2^n - 1): seq(a(n), n=1..32); # Zerinvary Lajos, Oct 05 2007
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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,easy,nice
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AUTHOR
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STATUS
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approved
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