OFFSET
1,1
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
PROG
(PARI) isok(n) = !isprime(n) && (quaddisc(n) == 4*n); \\ Michel Marcus, Nov 26 2013
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Aug 10 2002
STATUS
approved