|
%I #32 Mar 19 2020 11:21:43
%S 45,63,75,81,99,105,117,135,147,153,165,171,175,189,195,207,225,231,
%T 243,245,255,261,273,275,279,285,297,315,325,333,345,351,357,363,369,
%U 375,385,387,399,405,423,425,429,435,441,455,459,465,475
%N Odd numbers k such that k is the product of 2 numbers greater than one, in two or more ways.
%C Odd numbers that are not 1, a prime, the square or cube of a prime, or the product of two primes. - _Robert Israel_, Mar 19 2020
%H Robert Israel, <a href="/A333326/b333326.txt">Table of n, a(n) for n = 1..10000</a>
%e For n=2 the a(2) = 63 because 63 = 3 * 21 and 7 * 9.
%p select(t -> numtheory:-tau(t) >= 5, [seq(i,i=3..1000,2)]); # _Robert Israel_, Mar 19 2020
%t Select[2 * Range[250] + 1, DivisorSigma[0, #] > 4 &] (* _Amiram Eldar_, Mar 15 2020 *)
%o (PARI) forcomposite(n=4, 475, if(n%2 == 0, next()); if(numdiv(n) >= 5, print1(n,", "))); \\ _Joerg Arndt_, Mar 15 2020
%Y Cf. A005408, A058080, A226025.
%K nonn
%O 1,1
%A _Dimitris Valianatos_, Mar 15 2020
|
