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 A197121 #10 May 10 2025 02:30:14
%S A197121 21,69,77,84,93,133,165,189,205,213,221,237,253,276,285,301,308,309,
%T A197121 336,341,357,372,413,429,437,453,469,501,517,525,532,581,589,597,621,
%U A197121 645,660,669,693,717,741,749,756,789,805,820,837,852,861,869,884,893,917
%N A197121 Nonsquare positive integers n such that the fundamental unit of quadratic field Q(sqrt(d))has norm 1 and minimum one from two parts of fundamental unit are not integer.
%C A197121 Numbers that occur in A087643 and not in A194366.
%t A197121 cr = {}; Do[If[IntegerQ[Sqrt[n]], , kk = NumberFieldFundamentalUnits[Sqrt[n]]; d1 = kk[[1]][[2]][[1]]; d2 = kk[[1]][[1]] kk[[1]][[2]][[2]]; d3 = Expand[(d1 + d2) (d1 - d2)]; If[d3 == 1, k1 = Max[Denominator[d1], Denominator[d2]]; If[k1 == 1, , AppendTo[cr, n]]]], {n, 2, 2000}]; cr
%Y A197121 Cf. A087643, A172000, A194366, A197115.
%K A197121 nonn
%O A197121 1,1
%A A197121 _Artur Jasinski_, Oct 10 2011