A071929 Numbers k such that the sum of exponents of k is equal to the greatest prime factor of k; a(1)=1.

1, 4, 12, 18, 27, 80, 120, 180, 200, 270, 300, 405, 448, 450, 500, 672, 675, 750, 1008, 1120, 1125, 1250, 1512, 1568, 1680, 1875, 2268, 2352, 2520, 2800, 3125, 3402, 3528, 3780, 3920, 4200, 5103, 5292, 5488, 5670, 5880, 6300, 7000, 7938, 8232, 8505, 8820

Offset

1,2

Links

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

Example

28160 is a term since 28160 = 2^9*5^1*11^1 and 9+1+1 = 11 and Gpf(28160) = 11.

Mathematica

Select[Range[10^4], (f = FactorInteger[#])[[-1, 1]] == Plus @@ f[[;; , 2]] &] (* Amiram Eldar, Dec 08 2019 *)

Crossrefs

Cf. A006530, A086436.

Sequence in context: A340597 A325234 A075867 * A008037 A301251 A367397

Adjacent sequences: A071926 A071927 A071928 * A071930 A071931 A071932

Keyword

nonn

Author

Jason Earls, Jun 14 2002

Status

approved