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

Terms

a(0) =0a(1) =1a(2) =16a(3) =64a(4) =196a(5) =441a(6) =900a(7) =1600a(8) =2704a(9) =4225a(10) =6400a(11) =9216a(12) =12996a(13) =17689a(14) =23716a(15) =30976a(16) =40000a(17) =50625a(18) =63504a(19) =78400a(20) =96100a(21) =116281a(22) =139876a(23) =166464a(24) =197136a(25) =231361a(26) =270400a(27) =313600a(28) =362404a(29) =416025