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Search: id:A103340
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| A103340 |
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Denominator of the unitary harmonic mean (i.e. the harmonic mean of the unitary divisors) of the positive integer n. |
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+0
2
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| 1, 3, 2, 5, 3, 1, 4, 9, 5, 9, 6, 5, 7, 3, 2, 17, 9, 5, 10, 3, 8, 9, 12, 3, 13, 21, 14, 5, 15, 3, 16, 33, 4, 27, 12, 25, 19, 15, 14, 27, 21, 2, 22, 15, 1, 9, 24, 17, 25, 39, 6, 35, 27, 7, 18, 9, 20, 45, 30, 1, 31, 12, 20, 65, 21, 3, 34, 45, 8, 9, 36, 5, 37, 57, 26, 25, 24, 7, 40, 51, 41, 63
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OFFSET
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1,2
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EXAMPLE
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1,4/3,3/2,8/5,5/3,2,
a(8)=9 because the unitary divisors of 8 are {1,8} and 2/(1/1+1/8)=16/9.
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MAPLE
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with(numtheory): udivisors:=proc(n) local A, k: A:={}: for k from 1 to tau(n) do if gcd(divisors(n)[k], n/divisors(n)[k])=1 then A:=A union {divisors(n)[k]} else A:=A fi od end: utau:=n->nops(udivisors(n)): usigma:=n->sum(udivisors(n)[j], j=1..nops(udivisors(n))): uH:=n->n*utau(n)/usigma(n):seq(denom(uH(n)), n=1..90);
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CROSSREFS
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Cf. A103339, A099377, A099378.
Adjacent sequences: A103337 A103338 A103339 this_sequence A103341 A103342 A103343
Sequence in context: A046227 A120842 A152178 this_sequence A106615 A130299 A143309
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KEYWORD
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frac,nonn
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AUTHOR
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Emeric Deutsch (deutsch(AT)duke.poly.edu), Jan 31 2005
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