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A161818
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If b(n) = the largest proper divisor of n, then a(n) = (2^n - 1)/(2^b(n) - 1).
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1
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3, 7, 5, 31, 9, 127, 17, 73, 33, 2047, 65, 8191, 129, 1057, 257, 131071, 513, 524287, 1025, 16513, 2049, 8388607, 4097, 1082401, 8193, 262657, 16385, 536870911, 32769, 2147483647, 65537, 4196353, 131073, 270549121, 262145, 137438953471, 524289
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OFFSET
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2,1
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LINKS
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EXAMPLE
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MAPLE
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with(numtheory): a := proc (n) options operator, arrow: (2^n-1)/(2^divisors(n)[tau(n)-1]-1) end proc: seq(a(n), n = 2 .. 40); # Emeric Deutsch, Jun 26 2009
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MATHEMATICA
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b[n_] := Divisors[n][[-2]];
a[n_] := (2^n - 1)/(2^b[n] - 1);
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PROG
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(PARI) a(n) = my(d=divisors(n)); (2^n-1)/(2^d[#d-1]-1); \\ Michel Marcus, Nov 20 2020
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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