OFFSET
1,2
COMMENTS
There are A000041(k) distinct prime signatures of length k. - David A. Corneth, Apr 25 2020
A square k is a term iff k belongs to A062503; in this case, k = p_1^2 * p_2^2 *...* p_r^2 and bigomega(k) = 2*omega(k) = 2*r. - Bernard Schott, Apr 25 2020
LINKS
Enrique Pérez Herrero, Table of n, a(n) for n = 1..5000
MATHEMATICA
Select[Range[700], PrimeOmega[#] == 2*PrimeNu[#] &] (* Jean-François Alcover, Jun 29 2013 *)
PROG
(PARI) is(n)=my(f=factor(n)[, 2]); vecsum(f)==2*#f \\ Charles R Greathouse IV, Oct 15 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Feb 07 2002
STATUS
approved