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 A218042 #8 Feb 16 2025 08:33:18 %S A218042 1111,1226,2031,2335,2362,2602,2986,3129,3246,3379,3585,3598,3599, %T A218042 3722,3782,3966,4097,4321,4334,4359,4555,4582,4586,4843,4865,4867, %U A218042 5071,5611,5615,5630,5631,5777,6071,6078,6085,6087,6202,6239,6294,6395,6574,6854,6891 %N A218042 Numbers n such that Q(sqrt(n)) has class number 10. %H A218042 Charles R Greathouse IV, <a href="/A218042/b218042.txt">Table of n, a(n) for n = 1..10000</a> %H A218042 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ClassNumber.html">Class Number</a> %t A218042 Select[Range[6891], SquareFreeQ[#] && NumberFieldClassNumber@Sqrt[#] == 10 &] %o A218042 (PARI) is(n)=issquarefree(n) && qfbclassno(if(n%4>1,4,1)*n)==10 \\ _Charles R Greathouse IV_, Jan 19 2017 %Y A218042 Cf. A003172, A029702-A029705, A218038-A218041. %K A218042 nonn %O A218042 1,1 %A A218042 _Arkadiusz Wesolowski_, Oct 19 2012