A225530 Number of ordered pairs (i,j) with i,j >= 0, i + j = n and gcd(i,j) <= 1.

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, 28, 8, 30, 16, 20, 16, 24, 12, 36, 18, 24, 16, 40, 12, 42, 20, 24, 22, 46, 16, 42, 20, 32, 24, 52, 18, 40, 24, 36, 28, 58, 16, 60, 30, 36, 32, 48, 20, 66

Offset: 0

Author

Robert Price, May 09 2013

Keywords

• nonn
• easy

Comments

This sequence is in reply to an extension request made in A100449.

Note that gcd(0,m) = m for any m.

Apparently a(n) = A000010(n), n >= 2. - R. J. Mathar, May 11 2013

Links

• Robert Price, Table of n, a(n) for n = 0..400

Crossrefs

Cf. A018805, A027430, A100448, A100449, A100450, A213207, A213208, A213212, A213213.

Programs

Mathematica

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}]