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A038199
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Row sums of triangle T(m,n) = number of solutions to 1 <= a(1) < a(2) < ... < a(m) <= n, where gcd(a(1), a(2), ..., a(m), n) = 1, in A020921.
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13
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1, 2, 6, 12, 30, 54, 126, 240, 504, 990, 2046, 4020, 8190, 16254, 32730, 65280, 131070, 261576, 524286, 1047540, 2097018, 4192254, 8388606, 16772880, 33554400, 67100670, 134217216, 268419060, 536870910, 1073708010, 2147483646
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OFFSET
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1,2
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COMMENTS
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The function T(m,n) described above has an inverse: see A038200.
Also, Moebius transform of 2^n - 1 = A000225. Also, number of rationals in [0, 1) whose binary expansions consist just of repeating bits of (least) period exactly n (i.e., there's no preperiodic part), where 0 = 0.000... is considered to have period 1. - Brad Chalfan (brad(AT)chalfan.net), May 29 2006
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LINKS
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FORMULA
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a(n) = Sum_{d | n} mu(n/d)*(2^d-1). - Paul Barry, Mar 20 2005
Lambert g.f.: Sum_{n>=1} a(n)*x^n/(1 - x^n) = x/((1 - x)*(1 - 2*x)). - Ilya Gutkovskiy, Apr 25 2017
O.g.f.: Sum_{d >= 1} mu(d)*(x^d/((1 - x^d)*(1 - 2*x^d)). - Petros Hadjicostas, Jun 18 2019
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MATHEMATICA
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Table[Plus@@((2^Divisors[n]-1)MoebiusMu[n/Divisors[n]]), {n, 1, 31}] (* Brad Chalfan (brad(AT)chalfan.net), May 29 2006 *)
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PROG
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(Haskell)
a038199 n = sum [a008683 (n `div` d) * (a000225 d)| d <- a027750_row n]
(Python)
from sympy import mobius, divisors
def a(n): return sum(mobius(n//d) * (2**d - 1) for d in divisors(n))
(PARI) a(n) = sumdiv(n, d, moebius(n/d)*(2^d-1)); \\ Michel Marcus, Jun 28 2017
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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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Temba Shonhiwa (Temba(AT)maths.uz.ac.zw)
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EXTENSIONS
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More terms from Brad Chalfan (brad(AT)chalfan.net), May 29 2006
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STATUS
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approved
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