OFFSET
1,1
COMMENTS
Close to A065036 but not the same. One of several quasi-square classes.
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..1000
FORMULA
n = prod( p(i)^e(i)) i in [1, k] => sum( e(i)), i in [1, k] == 2k
EXAMPLE
240=2^4*3*5 so there are 3 distinct prime factors, sum of exponents is 6=2*3 and 240 is not a square so is in the list.
MATHEMATICA
Select[Range[1000], !IntegerQ[Sqrt[#]]&&PrimeOmega[#]==2*PrimeNu[#]&] (* Harvey P. Dale, Jul 05 2023 *)
PROG
(PARI) n=0; for (m=1, 10^9, if (issquare(m), next); if (bigomega(m) == 2*omega(m), write("b065127.txt", n++, " ", m); if (n==1000, return))) \\ Harry J. Smith, Oct 12 2009
(PARI) is(n)=my(f=factor(n)); issquare(n) && bigomega(f)==2*omega(f) \\ Charles R Greathouse IV, Oct 15 2015; corrected by Michel Marcus, Apr 25 2020
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Olivier Gérard, Nov 14 2001
EXTENSIONS
OFFSET changed from 0 to 1 by Harry J. Smith, Oct 11 2009
STATUS
approved