OFFSET
1,1
REFERENCES
David A. Cox, "Primes of the Form x^2 + n y^2", Wiley, 1989, p. 60.
G. B. Mathews, Theory of Numbers, Chelsea, no date, p. 263.
PROG
(PARI) ok(n)={my(u=quadclassunit(-4*n).cyc); #u==2 && !select(t->t<>2, u)} \\ Andrew Howroyd, Jun 09 2018
CROSSREFS
KEYWORD
nonn,fini,full
AUTHOR
STATUS
approved