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 A225530 #15 Aug 02 2019 03:25:05
%S A225530 1,2,1,2,2,4,2,6,4,6,4,10,4,12,6,8,8,16,6,18,8,12,10,22,8,20,12,18,12,
%T A225530 28,8,30,16,20,16,24,12,36,18,24,16,40,12,42,20,24,22,46,16,42,20,32,
%U A225530 24,52,18,40,24,36,28,58,16,60,30,36,32,48,20,66
%N A225530 Number of ordered pairs (i,j) with i,j >= 0, i + j = n and gcd(i,j) <= 1.
%C A225530 This sequence is in reply to an extension request made in A100449.
%C A225530 Note that gcd(0,m) = m for any m.
%C A225530 Apparently a(n) = A000010(n), n >= 2. - _R. J. Mathar_, May 11 2013
%H A225530 Robert Price, <a href="/A225530/b225530.txt">Table of n, a(n) for n = 0..400</a>
%t A225530 f[n_]:=Length[Complement[Union[Flatten[Table[If[i+j==n&&GCD[i, j]<=1, {i,j}], {i, 0, n}, {j, 0, n}], 1]], {Null}]]; Table[f[n], {n, 0, 100}]
%Y A225530 Cf. A018805, A027430, A100448, A100449, A100450, A213207, A213208, A213212, A213213.
%K A225530 nonn,easy
%O A225530 0,2
%A A225530 _Robert Price_, May 09 2013