A072901 Composite numbers n such that the discriminant of the quadratic field Q(sqrt(n)) equals 4n.

6, 10, 14, 15, 22, 26, 30, 34, 35, 38, 39, 42, 46, 51, 55, 58, 62, 66, 70, 74, 78, 82, 86, 87, 91, 94, 95, 102, 106, 110, 111, 114, 115, 118, 119, 122, 123, 130, 134, 138, 142, 143, 146, 154, 155, 158, 159, 166, 170, 174, 178, 182, 183, 186, 187, 190, 194, 195

Offset: 1

Author

Benoit Cloitre, Aug 10 2002

Keywords

• easy
• nonn

Comments

Conjecture: All terms are squarefree. Example: 6=2*3; 15=3*5; 30=2*3*5; 154=2*7*11; 195=3*5*13. - Vincenzo Librandi, Aug 08 2010 and Michel Marcus, Nov 26 2013

If prime numbers were accepted, then sequence A230375 would have been obtained. - Michel Marcus, Nov 26 2013

Links

• Wikipedia, Quadratic field

Crossrefs

Cf. A037449.

Programs

PARI

isok(n) = !isprime(n) && (quaddisc(n) == 4*n); \\ Michel Marcus, Nov 26 2013