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A046018 Discriminants of imaginary quadratic fields with class number 21 (negated). 6
431, 503, 743, 863, 1931, 2503, 2579, 2767, 2819, 3011, 3371, 4283, 4523, 4691, 5011, 5647, 5851, 5867, 6323, 6691, 7907, 8059, 8123, 8171, 8243, 8387, 8627, 8747, 9091, 9187, 9811, 9859, 10067, 10771, 11731, 12107, 12547, 13171, 13291 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

85 discriminants in this sequence (proved).

LINKS

Giovanni Resta, Table of n, a(n) for n = 1..85 (full sequence, from Weisstein's World of Mathematics)

Steven Arno, M. L. Robinson, Ferrell S. Wheeler, Imaginary quadratic fields with small odd class number, Acta Arith. 83 (1998) 295-330.

Duncan A. Buell, Small class numbers and extreme values of L-functions of quadratic fields, Math. Comp., 31 (1977), 786-796.

Keith Matthews, Tables of imaginary quadratic fields with small class numbers

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 < 14000, n++, s = Sqrt[-n]; If[ NumberFieldClassNumber[s] == 21, d = -NumberFieldDiscriminant[s]; Print[d]; Sow[d]]]][[2, 1]] // Union (* Jean-Fran├žois Alcover, Oct 05 2012 *)

CROSSREFS

Cf. A006203, A013658, A014602, A014603, A046002 - A046020.

Sequence in context: A176387 A160518 A273807 * A142802 A003548 A179173

Adjacent sequences:  A046015 A046016 A046017 * A046019 A046020 A046021

KEYWORD

nonn,fini,full

AUTHOR

Eric W. Weisstein

STATUS

approved

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Last modified January 15 20:47 EST 2019. Contains 319184 sequences. (Running on oeis4.)