MATHEMATICA
f[n_] := Denominator[Sum[1/(2^i - 1), {i, n}]]; Array[f, 16] (* _Robert G. Wilson v, _, May 25 2011 *)
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f[n_] := Denominator[Sum[1/(2^i - 1), {i, n}]]; Array[f, 16] (* _Robert G. Wilson v, _, May 25 2011 *)
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a:= n -> denom(add(1/(2^i-1), i=1..n)); \\ _// _Robert Israel_, Dec 28 2012
a(n) = a(n-1) (2^n - 1)/gcd(a(n-1) (2^n-1), (2^n-1) A087689(n-1) + a(n-1)). - _Robert Israel_, Dec 28 2012
a:= n -> denom(add(1/(2^i-1), i=1..n)); \\ _Robert Israel_, Dec 28 2012
B-file, Maple program and comment corrected by Robert Israel, Dec 28 2012
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Least common denominators of A000225.
Robert Israel, <a href="/A087690/b087690.txt">Table of n, a(n) for n = 1..103</a>
a(n) = a(n-1) (2^n - 1)/gcd(a(n-1) (2^n-1), (2^n-1) A087689(n-1) + a(n-1))
a:= n -> denom(add(1/(2^i-1), i=1..n));
B-file, Maple program and comment corrected by Robert Israel, Dec 28 2012
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a(n) = lcm(a(n-1), 2^n-1)
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