Number of ordered quadruples of integers from [ 2,n ] with no global factor.

Terms

a(0) =0a(1) =3a(2) =9a(3) =28a(4) =50a(5) =105a(6) =169a(7) =279a(8) =406a(9) =625a(10) =839a(11) =1202a(12) =1570a(13) =2086a(14) =2646a(15) =3461a(16) =4219a(17) =5358a(18) =6452a(19) =7899a(20) =9381a(21) =11404a(22) =13240a(23) =15805a(24) =18272a(25) =21383a(26) =24461a(27) =28520a(28) =32107a(29) =37066