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

Terms

a(0) =0a(1) =0a(2) =0a(3) =8a(4) =28a(5) =63a(6) =150a(7) =280a(8) =468a(9) =780a(10) =1200a(11) =1728a(12) =2508a(13) =3458a(14) =4620a(15) =6160a(16) =8000a(17) =10125a(18) =12852a(19) =15960a(20) =19530a(21) =23870a(22) =28798a(23) =34272a(24) =40848a(25) =48100a(26) =56160a(27) =65520a(28) =75852a(29) =87075