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A103339
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Numerator of the unitary harmonic mean (i.e. the harmonic mean of the unitary divisors) of the positive integer n.
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1
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1, 4, 3, 8, 5, 2, 7, 16, 9, 20, 11, 12, 13, 7, 5, 32, 17, 12, 19, 8, 21, 22, 23, 8, 25, 52, 27, 14, 29, 10, 31, 64, 11, 68, 35, 72, 37, 38, 39, 80, 41, 7, 43, 44, 3, 23, 47, 48, 49, 100, 17, 104, 53, 18, 55, 28, 57, 116, 59, 4, 61, 31, 63, 128, 65, 11, 67, 136, 23, 35, 71, 16, 73
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| 1,4/3,3/2,8/5,5/3,2,
a(8)=16 because the unitary divisors of 8 are {1,8} and 2/(1/1+1/8)=16/9.
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MAPLE
| 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(numer(uH(n)), n=1..81);
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CROSSREFS
| Cf. A103340, A099377, A099378.
Sequence in context: A200345 A021962 A097672 * A092383 A156028 A021232
Adjacent sequences: A103336 A103337 A103338 * A103340 A103341 A103342
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KEYWORD
| frac,nonn
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AUTHOR
| Emeric Deutsch (deutsch(AT)duke.poly.edu), Jan 31 2005
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