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

Terms

a(0) =0a(1) =0a(2) =0a(3) =7a(4) =24a(5) =76a(6) =162a(7) =333a(8) =576a(9) =976a(10) =1500a(11) =2275a(12) =3240a(13) =4572a(14) =6174a(15) =8281a(16) =10752a(17) =13888a(18) =17496a(19) =21951a(20) =27000a(21) =33100a(22) =39930a(23) =48037a(24) =57024a(25) =67536a(26) =79092a(27) =92443a(28) =107016a(29) =123676