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A138223
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a(n) = the nearest divisor of n to the number of positive divisors of n. In case of tie, round up.
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4
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1, 2, 3, 4, 1, 3, 1, 4, 3, 5, 1, 6, 1, 2, 5, 4, 1, 6, 1, 5, 3, 2, 1, 8, 5, 2, 3, 7, 1, 10, 1, 8, 3, 2, 5, 9, 1, 2, 3, 8, 1, 7, 1, 4, 5, 2, 1, 12, 1, 5, 3, 4, 1, 9, 5, 8, 3, 2, 1, 12, 1, 2, 7, 8, 5, 6, 1, 4, 3, 7, 1, 12, 1, 2, 5, 4, 7, 6, 1, 10, 3, 2, 1, 12, 5, 2, 3, 8, 1, 10, 7, 4, 3, 2, 5, 12, 1, 7, 9, 10, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| There are four positive divisors of 15: (1,3,5,15). There are two divisors, 3 and 5, that are nearest 4. We take the larger divisor, 5 in this case, in case of a tie; so a(15) = 5.
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MAPLE
| A138223 := proc(n) if n = 1 then RETURN(1); fi; t := numtheory[tau](n) ; dvs := sort(convert(numtheory[divisors](n), list)) ; a := op(-1, dvs) ; for i from 2 to nops(dvs) do if abs(op(-i, dvs) - t) < abs(a-t) then a := op(-i, dvs) ; fi; od: a ; end: seq(A138223(n), n=1..120) ; [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 20 2009]
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CROSSREFS
| Cf. A138221, A138222, A138224, A000005.
Sequence in context: A074057 A163258 A141063 * A194742 A159798 A003324
Adjacent sequences: A138220 A138221 A138222 * A138224 A138225 A138226
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Mar 06 2008
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EXTENSIONS
| Extended beyond a(15) by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 20 2009
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