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) =9a(3) =49a(4) =144a(5) =361a(6) =729a(7) =1369a(8) =2304a(9) =3721a(10) =5625a(11) =8281a(12) =11664a(13) =16129a(14) =21609a(15) =28561a(16) =36864a(17) =47089a(18) =59049a(19) =73441a(20) =90000a(21) =109561a(22) =131769a(23) =157609a(24) =186624a(25) =219961a(26) =257049a(27) =299209a(28) =345744a(29) =398161