Number of (w,x,y,z) with all terms in {1,...,n} and w*x+y*z<=n^2.

Terms

a(0) =0a(1) =0a(2) =9a(3) =56a(4) =196a(5) =499a(6) =1074a(7) =2014a(8) =3497a(9) =5658a(10) =8705a(11) =12811a(12) =18278a(13) =25239a(14) =34099a(15) =45086a(16) =58543a(17) =74748a(18) =94210a(19) =117123a(20) =144094a(21) =175386a(22) =211549a(23) =252962a(24) =300400a(25) =353941a(26) =414476a(27) =482417a(28) =558525a(29) =643076