A115024 Natural numbers n such that the number of prime factors of n (counted with multiplicity) is equal to the number of decimal digits of n.

2, 3, 5, 7, 10, 14, 15, 21, 22, 25, 26, 33, 34, 35, 38, 39, 46, 49, 51, 55, 57, 58, 62, 65, 69, 74, 77, 82, 85, 86, 87, 91, 93, 94, 95, 102, 105, 110, 114, 116, 117, 124, 125, 130, 138, 147, 148, 153, 154, 164, 165, 170, 171, 172, 174, 175, 182, 186, 188, 190, 195

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

25 = 5*5 and 25 has two digits.
116 = 2*2*29 and 116 has three digits.

Mathematica

Select[Range[2, 300], Sum[FactorInteger[ # ][[i]][[2]], {i, 1, Length[FactorInteger[ # ]]}] == Floor[Log[10, # ] + 1] &] (* Stefan Steinerberger, Feb 27 2006 *)
Select[Range[200], PrimeOmega[#]==IntegerLength[#]&] (* Harvey P. Dale, Jul 28 2020 *)

Prog

(PARI) is(n)=#Str(n)==bigomega(n) \\ Charles R Greathouse IV, Feb 04 2013

Crossrefs

Cf. A165256, A167050.

Sequence in context: A064480 A274111 A209000 * A167050 A308388 A019529

Adjacent sequences: A115021 A115022 A115023 * A115025 A115026 A115027

Keyword

base,easy,nonn

Author

Giovanni Teofilatto, Feb 24 2006

Extensions

More terms from Stefan Steinerberger, Feb 27 2006

Status

approved