login
A067547
Number of divisors of n equals the average of distinct prime factors of n.
1
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
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
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Jan 28 2002
EXTENSIONS
More terms from Naohiro Nomoto, Mar 01 2002
STATUS
approved