Number of (w,x,y,z) with all terms in {1,...,n} and w<=2x and y<3z.

Terms

a(0) =0a(1) =1a(2) =16a(3) =64a(4) =196a(5) =462a(6) =930a(7) =1680a(8) =2860a(9) =4485a(10) =6800a(11) =9888a(12) =13908a(13) =19019a(14) =25564a(15) =33440a(16) =43200a(17) =54900a(18) =68796a(19) =85120a(20) =104470a(21) =126511a(22) =152218a(23) =181560a(24) =214896a(25) =252525a(26) =295360a(27) =342720a(28) =396116a(29) =455370