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 A056987 Discriminants of imaginary quadratic fields with class number 25 (negated). 20
 479, 599, 1367, 2887, 3851, 4787, 5023, 5503, 5843, 7187, 7283, 7307, 7411, 8011, 8179, 9227, 9923, 10099, 11059, 11131, 11243, 11867, 12211, 12379, 12451, 12979, 14011, 14923, 15619, 17483, 18211, 19267, 19699, 19891, 20347, 21107, 21323 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Sequence contains 95 members; largest is 93307. The class group of Q[sqrt(-d)] is isomorphic to C_5 X C_5 for d = 12451 and 37363. For all other d in this sequence, the class group of Q[sqrt(-d)] is isomorphic to C_25. - Jianing Song, Dec 01 2019 LINKS Jianing Song, Table of n, a(n) for n = 1..95 Eric Weisstein's World of Mathematics, Class Number. MATHEMATICA Reap[ For[n = 1, n < 22000, n++, s = Sqrt[-n]; If[ NumberFieldClassNumber[s] == 25, d = -NumberFieldDiscriminant[s]; Print[d]; Sow[d]]]][[2, 1]] // Union (* Jean-François Alcover, Oct 05 2012 *) CROSSREFS Cf. A014602, A014603, A006203, A013658, A046002, A046003, A046004, A046005, A046006, A046007, A046008, A046009, A046010, A046011, A046012, A046013, A046014, A046015, A046016, A123563, A046018, A171724, A046020, A048925. Sequence in context: A252542 A122268 A186950 * A323051 A025025 A108256 Adjacent sequences: A056984 A056985 A056986 * A056988 A056989 A056990 KEYWORD nonn,fini,full AUTHOR Eric W. Weisstein STATUS approved

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Last modified August 7 01:21 EDT 2024. Contains 375002 sequences. (Running on oeis4.)