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 A355878 #13 Jul 20 2022 08:49:20 %S A355878 5,229,401,577,1129,1297,8101,11321,11257,18229,7057,23593,27689,8761, %T A355878 56857,146077,63361,25601,24337,55441,439573,14401,32401,78401,70969, %U A355878 69697,376897,106537,41617,160001,193601,57601,197137,367721,414433,1432813,444089,331777 %N A355878 Smallest p == 1 (mod 4) such that Q(sqrt(p)) has class number 2n+1. %C A355878 Also smallest odd prime p such that Q(sqrt(p)) has narrow class number (also called form class number) 2n+1. %C A355878 Conjecture: a(n) > A002148(n) for all n. %H A355878 Wikipedia, <a href="http://en.wikipedia.org/wiki/Class_number_(number_theory)#Class_numbers_of_quadratic_fields">Class numbers of quadratic fields</a> %H A355878 <a href="/index/Qua#quadfield">Index entries for sequences related to quadratic fields</a> %F A355878 a(n) = min(A355876(n),A355877(n)). %e A355878 p = 229 is the smallest odd prime such that Q(sqrt(p)) has class number 3, so a(1) = 229. %o A355878 (PARI) a(n) = forprime(p=2, oo, if(p%4==1 && qfbclassno(p)==2*n+1, return(p))) %Y A355878 Cf. A355876, A355877. %K A355878 nonn %O A355878 0,1 %A A355878 _Jianing Song_, Jul 20 2022