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 A351665 Discriminants of imaginary quadratic fields with class number 27 (negated). 1
 983, 1231, 1399, 1607, 1759, 1879, 1999, 3271, 3299, 3943, 4903, 6007, 6011, 7699, 8867, 10531, 10939, 11003, 11027, 11383, 11491, 11779, 11939, 13411, 14243, 14723, 15107, 15739, 16411, 16547, 17443, 17627, 17659, 17747, 18587, 18787, 18859, 19051, 19427 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Sequence contains 93 terms; largest is 103387. The class group of Q[sqrt(-d)] is isomorphic to C_9 X C_3 for d = 3299, 19427, 34603, 89923, and 98443. For all other d in this sequence, the class group of Q[sqrt(-d)] is isomorphic to C_27. LINKS Andy Huchala, Table of n, a(n) for n = 1..93 Eric Weisstein's World of Mathematics, Class Number PROG (Sage) ls = [(QuadraticField(-n, 'a').discriminant(), QuadraticField(-n, 'a').class_number()) for n in (0..10000) if is_fundamental_discriminant(-n) and not is_square(n)]; [-a[0] for a in ls if a[1] == 27] (PARI) isok(n) = {isfundamental(-n) && quadclassunit(-n).no == 27}; \\ Michel Marcus, Mar 02 2022 CROSSREFS Cf. A006203, A013658, A014602, A014603, A046002-A046020, A046125, A056987, A351664. Sequence in context: A122472 A252402 A087907 * A182574 A096701 A345539 Adjacent sequences: A351662 A351663 A351664 * A351666 A351667 A351668 KEYWORD nonn,fini,full AUTHOR Andy Huchala, Feb 16 2022 STATUS approved

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Last modified September 27 00:17 EDT 2023. Contains 365669 sequences. (Running on oeis4.)