Number of (j,k): j+k=n, (j,n)=(k,n)=1, j,k squarefree.

Terms

a(0) =0a(1) =1a(2) =2a(3) =2a(4) =2a(5) =2a(6) =4a(7) =4a(8) =2a(9) =2a(10) =4a(11) =4a(12) =6a(13) =4a(14) =4a(15) =6a(16) =8a(17) =6a(18) =6a(19) =6a(20) =4a(21) =8a(22) =8a(23) =8a(24) =8a(25) =8a(26) =8a(27) =6a(28) =10a(29) =8