A152617 - OEIS

A152617

Smallest number m such that m has exactly n distinct prime factors and sigma(m) has exactly n distinct prime factors.

%I #5 Mar 30 2012 17:35:01

%S 2,6,60,1140,22230,778050,28787850,1237877550,82937795850,

%T 6054459097050,802693813972050,126022928793611850

%N Smallest number m such that m has exactly n distinct prime factors and sigma(m) has exactly n distinct prime factors.

%C a(13) <= 20541737393358731550. a(14) <= 3553720569051060558150. - Donovan Johnson, Jul 13 2011

%e a(9) = 82937795850 = 2*3^2*5^2*7*13*19*37*43*67 (9 distinct prime factors). Sigma(82937795850) = 307906959360 = 2^11*3*5*7*11*13*17*19*31 (9 distinct prime factors).

%Y Cf. A000203, A001221.

%K nonn

%O 1,1

%A _Donovan Johnson_, Dec 13 2008

%E a(12) from _Donovan Johnson_, Jul 13 2011