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 A260335 #11 Feb 17 2021 04:19:45 %S A260335 79,223,359,439,443,499,659,727,839,1087,1091,1171,1223,1327,1367, %T A260335 1523,1567,1627,1787,1811,1847,1907,1987,2027,2099,2143,2207,2251, %U A260335 2399,2459,2467,2543,2659,2711,2971,3023,3163,3251,3391,3719,3739,3803,3967,4139,4159,4271 %N A260335 Prime determinants of forms with class number > 2. %C A260335 Also primes p == 3 (mod 4) such that Z[sqrt(p)] = Z[x]/(x^2 - p) is not a unique factorization domain (or equivalently, not a principal ideal domain). - _Jianing Song_, Feb 17 2021 %H A260335 M. Suryanarayana, <a href="https://www.ias.ac.in/article/fulltext/seca/002/02/0178-0179">Positive determinants of binary quadratic forms whose class-number is 2</a>, Proceedings of the Indian Academy of Sciences. Section A, 2 (1935), 178-179. %o A260335 (PARI) isA260335(p) = isprime(p) && (p%4==3) && quadclassunit(4*p)[1] > 1 \\ _Jianing Song_, Feb 17 2021 %Y A260335 Cf. A002052. %K A260335 nonn,more %O A260335 1,1 %A A260335 _N. J. A. Sloane_, Jul 27 2015 %E A260335 More terms from _Jianing Song_, Feb 17 2021