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 A103249 #20 Nov 14 2019 17:52:13
%S A103249 3,12,17,27,48,63,68,75,77,99,108,147,153,192,243,252,272,300,301,308,
%T A103249 323,363,396,399,425,432,507,561,567,577,588,612,621,675,693,768,833,
%U A103249 867,891,943,972,1008,1023,1083,1088,1200,1204,1232,1292,1323,1377,1377
%N A103249 Numbers y, without duplication, in Pythagorean triples x,y,z where x,y,z are relatively prime composite numbers and x is a perfect square.
%C A103249 There exists no case in which x and y are both squares.
%H A103249 MathForFun, <a href="http://groups.yahoo.com/group/mathforfun/message/9962">Pythagorean triples</a>
%H A103249 Chenglong Zou, Peter Otzen, Cino Hilliard, <a href="/A103246/a103246.txt">Pythagorean triplets</a>, digest of 6 messages in mathfun Yahoo group, Mar 19, 2005.
%e A103249 y=3, x=4, 4^2 + 3^2 = 5^2. 3 is the 1st entry in the list.
%o A103249 (PARI) pythtrisq(n) = { local(a,b,c=0,k,x,y,z,vy,j); w = vector(n*n+1); for(a=1,n, for(b=1,n, x=2*a*b; y=b^2-a^2; z=b^2+a^2; if(y > 0 & issquare(x), c++; w[c]=y; print(x","y","z) ) ) ); vy=vector(c); w=vecsort(w); for(j=1,n*n, if(w[j]>0, k++; vy[k]=w[j]; ) ); for(j=1,200, print1(vy[j]",") ) }
%K A103249 easy,nonn
%O A103249 1,1
%A A103249 _Cino Hilliard_, Mar 19 2005