A067547 Number of divisors of n equals the average of distinct prime factors of n.

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

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

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.

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, # ] & ]

Crossrefs

Cf. A000005, A323171, A323172.

Sequence in context: A056724 A295732 A083174 * A166374 A083783 A162614

Adjacent sequences: A067544 A067545 A067546 * A067548 A067549 A067550

Keyword

nonn

Author

Joseph L. Pe, Jan 28 2002

Extensions

More terms from Naohiro Nomoto, Mar 01 2002

Status

approved