A033269 - OEIS

%I #11 Jun 10 2018 02:38:55

%S 840,1320,1365,1848

%N Numbers n such that every genus of binary quadratic forms of discriminant -4n consists of a single class and the class number h(-4n) = 16.

%D David A. Cox, "Primes of the Form x^2 + n y^2", Wiley, 1989, p. 60.

%D G. B. Mathews, Theory of Numbers, Chelsea, no date, p. 263.

%o (PARI) ok(n)={my(u=quadclassunit(-4*n).cyc); #u==4 && !select(t->t<>2, u)} \\ _Andrew Howroyd_, Jun 09 2018

%Y A subsequence of A000926.

%Y Cf. A033266, A033267, A033268.

%K nonn,fini,full

%O 1,1

%A _N. J. A. Sloane_