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A067547
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Number of divisors of n equals the average prime factor size of n.
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0
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2, 9, 15, 114, 170, 175, 245, 351, 372, 558, 580, 625, 1012, 1032, 1375, 1377, 1450, 1640, 2322, 3944, 4225, 4240, 4700, 4824, 5566, 5766, 5929, 6432, 6591, 6655, 7236, 8272, 8385, 8410, 9933, 10250, 10545, 11152, 11193, 11638, 13209, 14973, 15168
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| The prime factors of 15 are 3 and 5, having an average of 4. The number of divisors of 15 is also 4, so 15 is a term of the sequence.
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MATHEMATICA
| f[ n_ ] := FactorInteger[ n ]; g[ n_ ] := Module[ {a, l, t, r}, a = f[ n ]; l = Length[ a ]; t = Table[ a[ [ i ] ][ [ 1 ] ], {i, 1, l} ] ]; Select[ Range[ 2, 10^5 ], Mean[ g[ # ] ] == DivisorSigma[ 0, # ] & ]
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CROSSREFS
| Sequence in context: A108463 A056724 A083174 * A166374 A083783 A162614
Adjacent sequences: A067544 A067545 A067546 * A067548 A067549 A067550
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KEYWORD
| nonn
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AUTHOR
| Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jan 28 2002
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EXTENSIONS
| More terms from Naohiro Nomoto (n_nomoto(AT)yabumi.com), Mar 01 2002
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