Number of pairs of orthogonal (-x,y) vectors of length 1*(x+y), where x/y is the n-th rational <= 1, ordered first by y and then x, e.g. 1/1, 1/2, 1/3, 2/3, 1/4, 3/4 ...

A225986

Number of pairs of orthogonal (-x,y) vectors of length 1*(x+y), where x/y is the n-th rational <= 1, ordered first by y and then x, e.g. 1/1, 1/2, 1/3, 2/3, 1/4, 3/4 ...

Terms

    a(0) =4a(1) =9a(2) =20a(3) =60a(4) =45a(5) =420a(6) =102a(7) =378a(8) =1120a(9) =3024a(10) =231a(11) =22176a(12) =520a(13) =2376a(14) =8160a(15) =23760a(16) =63360a(17) =164736a(18) =1161a(19) =21780a(20) =185328a(21) =1235520a(22) =2570a(23) =14190a(24) =188760a(25) =544544a(26) =3660800a(27) =9335040a(28) =5643a(29) =147576

External references