# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a046015 Showing 1-1 of 1 %I A046015 #25 Feb 16 2025 08:32:38 %S A046015 335,519,527,679,1135,1172,1207,1383,1448,1687,1691,1927,2047,2051, %T A046015 2167,2228,2291,2315,2344,2644,2747,2859,3035,3107,3543,3544,3651, %U A046015 3688,4072,4299,4307,4568,4819,4883,5224,5315,5464,5492,5539,5899 %N A046015 Discriminants of imaginary quadratic fields with class number 18 (negated). %C A046015 The class group of Q[sqrt(-d)] is isomorphic to C_3 X C_6 for d = 9748, 12067, 16627, 17131, 19651, 22443, 23683, 34027, 34507. For all other known d in this sequence, the class group of Q[sqrt(-d)] is isomorphic to C_18. - _Jianing Song_, Dec 01 2019 %H A046015 Jianing Song, Table of n, a(n) for n = 1..150 %H A046015 Steven Arno, M. L. Robinson and Ferrel S. Wheeler, Imaginary quadratic fields with small odd class number, Acta Arithm. 83.4 (1998), 295-330 %H A046015 Duncan A. Buell, Small class numbers and extreme values of L-functions of quadratic fields, Math. Comp., 31 (1977), 786-796. %H A046015 C. Wagner, Class Number 5, 6 and 7, Math. Comput. 65, 785-800, 1996. %H A046015 Eric Weisstein's World of Mathematics, Class Number. %H A046015 Index entries for sequences related to quadratic fields %t A046015 Reap[ For[n = 1, n < 6000, n++, s = Sqrt[-n]; If[ NumberFieldClassNumber[s] == 18, d = -NumberFieldDiscriminant[s]; Print[d]; Sow[d]]]][[2, 1]] // Union (* _Jean-François Alcover_, Oct 05 2012 *) %Y A046015 Cf. A006203, A013658, A014602, A014603, A046002-A046020. %K A046015 nonn,fini,changed %O A046015 1,1 %A A046015 _Eric W. Weisstein_ # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE