OFFSET
1,1
COMMENTS
Odd numbers with at least two distinct prime factors. - N. J. A. Sloane, Oct 15 2022
Odd leg of more than one primitive Pythagorean triangles. For smallest odd leg common to 2^n PPTs, see A070826. - Lekraj Beedassy, Jul 12 2006
Numbers that can be factored by Shor's algorithm. - Charles R Greathouse IV, Mar 05 2012
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
FORMULA
a(n) ~ 2n. - Charles R Greathouse IV, Aug 20 2012
MAPLE
select(t -> nops(ifactors(t)[2]) > 1, [seq(2*i+1, i=1..1000)]); # Robert Israel, Dec 14 2014
MATHEMATICA
Select[Range[1, 249, 2], Length[FactorInteger[#]] > 1 &] (* Alonso del Arte, Jan 30 2012 *)
Select[ Range[1, 475, 2], PrimeNu@# > 1 &] (* Robert G. Wilson v, Dec 12 2014 *)
PROG
(ARIBAS): for k := 3 to 253 by 2 do ar := factorlist(k); if ar[0] < ar[length(ar)-1] then write(k, " ") end; end;
(PARI) is(n)=ispower(n, , &n); n%2&&!isprime(n)&&n>1 \\ Charles R Greathouse IV, Jan 30 2012
(PARI) is(n)=n%2 && !isprimepower(n) && n>1 \\ Charles R Greathouse IV, May 06 2016
(PARI) count(x)=if(x<9, 0, (x\=1) - sum(k=1, logint(x, 3), primepi(sqrtnint(x, k)) - 1) - x\2 - 1) \\ Charles R Greathouse IV, Mar 06 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jun 08 2001
EXTENSIONS
More terms from Klaus Brockhaus, Jun 10 2001
STATUS
approved