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 A063665 #9 Nov 07 2018 21:46:45
%S A063665 0,1,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,1,0,0,
%T A063665 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%U A063665 0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0
%N A063665 Number of ways 1/n can be written as 1/x^2 + 1/y^2 with y >= x >= 1.
%C A063665 Number of ordered pairs (x,y), with n = (x^2)(y^2)/(x^2 + y^2) and y >= x > 0. - _Antti Karttunen_, Nov 07 2018
%H A063665 Antti Karttunen, <a href="/A063665/b063665.txt">Table of n, a(n) for n = 1..100000</a>
%e A063665 a(90)=1 since 1/90 = 1/10^2 + 1/30^2
%e A063665 a(98)=2 since 1/98 = 1/10^2 + 1/70^2 = 1/14^2 + 1/14^2.
%e A063665 a(14400) = 3 since 1/14400 = 1/130^2 + 1/312^2 = 1/136^2 + 1/255^2 = 1/150^2 + 1/200^2. - _Antti Karttunen_, Nov 07 2018
%o A063665 (PARI) A063665(n) = { my(s=0); for(x=1,n,for(y=x,n,if((n*(x*x+y*y)) == (x*x*y*y), s++))); (s); }; \\ _Antti Karttunen_, Nov 07 2018
%o A063665 (PARI) A063665(n) = { my(s=0,y); for(x=sqrtint(n),n,my(x2=x*x); if((x2>n)&&issquare((n*x2)/(x2-n),&y)&&(1==denominator(y))&&(y>=x),s++)); (s); }; \\ _Antti Karttunen_, Nov 07 2018
%Y A063665 Cf. A000161, A025426, A018892, A063664.
%K A063665 nonn
%O A063665 1,98
%A A063665 _Henry Bottomley_, Jul 25 2001
%E A063665 Definition clarified by _Antti Karttunen_, Nov 07 2018