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 A276541 #9 Apr 10 2017 23:32:50 %S A276541 10,15,26,30,34,35,39,40,42,51,55,58,60,65,66,70,74,78,79,82,85,87,90, %T A276541 91,95,102,104,105,106,110,111,114,115,119,120,122,123,130,135,136, %U A276541 138,140,142,143,145,146,154,155,156,159,160,165,168,170,174,178,182 %N A276541 Positive integers n such that the ring of integers of Q(sqrt(n)) is not a UFD. %C A276541 Complement of A219361. %t A276541 Select[Range[210], NumberFieldClassNumber@Sqrt@# > 1 &] %Y A276541 Cf. A219361. %K A276541 nonn %O A276541 1,1 %A A276541 _Robert G. Wilson v_, Apr 09 2017