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A102187
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Arithmetic means of divisors of arithmetic numbers (arithmetic numbers, A003601, are those for which the average of the divisors is an integer).
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2
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1, 2, 3, 3, 4, 6, 7, 6, 6, 9, 10, 7, 8, 9, 12, 10, 15, 9, 16, 12, 12, 19, 15, 14, 21, 12, 22, 14, 13, 18, 24, 19, 18, 27, 15, 18, 15, 20, 30, 14, 31, 24, 21, 18, 34, 21, 24, 18, 36, 37, 24, 21, 40, 42, 27, 33, 30, 45, 28, 28, 32, 36, 30, 21, 49, 26, 51, 27, 52, 24, 54, 55, 27, 38
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Values of sigma(n)/tau(n) on the terms of A003601, where tau(n) (A000005) is the number of divisors of n and sigma(n) (A000203) is the sum of the divisors of n.
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REFERENCES
| O. Ore, On the averages of the divisors of a number, Amer. Math. Monthly, 55 (1948), 615-619.
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FORMULA
| a(n)=sigma(A003601(n))/tau(A003601(n)).
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EXAMPLE
| The first four terms are 1,2,3,amd 3, being the averages of the divisors of the first four arithmetic numbers, 1,3,5 and 6, respectively. Indeed, 1/1=1, (1+3)/2=2, (1+5)/2=3 and (1+2+3+6)/4=3.
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MAPLE
| with(numtheory): p:=proc(n) if type(sigma(n)/tau(n), integer)=true then sigma(n)/tau(n) else fi end: seq(p(n), n=1..130);
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CROSSREFS
| Cf. A003601, A000005, A000203.
Sequence in context: A188215 A023158 A120882 * A133610 A029033 A041003
Adjacent sequences: A102184 A102185 A102186 * A102188 A102189 A102190
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KEYWORD
| nonn
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AUTHOR
| Emeric Deutsch (deutsch(AT)duke.poly.edu), Feb 16 2005
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