This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A056987 #14 Feb 16 2025 08:32:43 %S A056987 479,599,1367,2887,3851,4787,5023,5503,5843,7187,7283,7307,7411,8011, %T A056987 8179,9227,9923,10099,11059,11131,11243,11867,12211,12379,12451,12979, %U A056987 14011,14923,15619,17483,18211,19267,19699,19891,20347,21107,21323 %N A056987 Discriminants of imaginary quadratic fields with class number 25 (negated). %C A056987 Sequence contains 95 members; largest is 93307. %C A056987 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 %H A056987 Jianing Song, <a href="/A056987/b056987.txt">Table of n, a(n) for n = 1..95</a> %H A056987 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ClassNumber.html">Class Number.</a> %t A056987 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 *) %Y A056987 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. %K A056987 nonn,fini,full %O A056987 1,1 %A A056987 _Eric W. Weisstein_