A333326 Odd numbers k such that k is the product of 2 numbers greater than one, in two or more ways.

45, 63, 75, 81, 99, 105, 117, 135, 147, 153, 165, 171, 175, 189, 195, 207, 225, 231, 243, 245, 255, 261, 273, 275, 279, 285, 297, 315, 325, 333, 345, 351, 357, 363, 369, 375, 385, 387, 399, 405, 423, 425, 429, 435, 441, 455, 459, 465, 475

Offset: 1

Author

Dimitris Valianatos, Mar 15 2020

Keywords

• nonn

Comments

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

Examples

			For n=2 the a(2) = 63 because 63 = 3 * 21 and 7 * 9.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A005408, A058080, A226025.

Programs

Maple

select(t -> numtheory:-tau(t) >= 5, [seq(i,i=3..1000,2)]); # Robert Israel, Mar 19 2020

Mathematica

Select[2 * Range[250] + 1, DivisorSigma[0, #] > 4 &] (* Amiram Eldar, Mar 15 2020 *)

PARI

forcomposite(n=4, 475, if(n%2 == 0, next()); if(numdiv(n) >= 5, print1(n,", "))); \\ Joerg Arndt, Mar 15 2020