The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A046015 Discriminants of imaginary quadratic fields with class number 18 (negated). 3
 335, 519, 527, 679, 1135, 1172, 1207, 1383, 1448, 1687, 1691, 1927, 2047, 2051, 2167, 2228, 2291, 2315, 2344, 2644, 2747, 2859, 3035, 3107, 3543, 3544, 3651, 3688, 4072, 4299, 4307, 4568, 4819, 4883, 5224, 5315, 5464, 5492, 5539, 5899 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 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 LINKS Jianing Song, Table of n, a(n) for n = 1..150 Steven Arno, M. L. Robinson and Ferrel S. Wheeler, Imaginary quadratic fields with small odd class number, Acta Arithm. 83.4 (1998), 295-330 Duncan A. Buell, Small class numbers and extreme values of L-functions of quadratic fields, Math. Comp., 31 (1977), 786-796. C. Wagner, Class Number 5, 6 and 7, Math. Comput. 65, 785-800, 1996. Eric Weisstein's World of Mathematics, Class Number. MATHEMATICA 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 *) CROSSREFS Cf. A006203, A013658, A014602, A014603, A046002-A046020. Sequence in context: A216138 A252995 A119760 * A184076 A253227 A105099 Adjacent sequences:  A046012 A046013 A046014 * A046016 A046017 A046018 KEYWORD nonn,fini AUTHOR STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 13 00:57 EDT 2021. Contains 344980 sequences. (Running on oeis4.)