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A046015 Discriminants of imaginary quadratic fields with class number 18 (negated).

%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, <a href="/A046015/b046015.txt">Table of n, a(n) for n = 1..150</a>
%H A046015 Steven Arno, M. L. Robinson and Ferrel S. Wheeler, <a href="http://matwbn.icm.edu.pl/ksiazki/aa/aa83/aa8341.pdf">Imaginary quadratic fields with small odd class number</a>, Acta Arithm. 83.4 (1998), 295-330
%H A046015 Duncan A. Buell, <a href="http://dx.doi.org/10.1090/S0025-5718-1977-0439802-X">Small class numbers and extreme values of L-functions of quadratic fields</a>, Math. Comp., 31 (1977), 786-796.
%H A046015 C. Wagner, <a href="http://dx.doi.org/10.1090/S0025-5718-96-00722-3">Class Number 5, 6 and 7</a>, Math. Comput. 65, 785-800, 1996.
%H A046015 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ClassNumber.html">Class Number.</a>
%H A046015 <a href="/index/Qua#quadfield">Index entries for sequences related to quadratic fields</a>
%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
%O A046015 1,1
%A A046015 _Eric W. Weisstein_