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) =12a(3) =56a(4) =168a(5) =418a(6) =837a(7) =1554a(8) =2640a(9) =4209a(10) =6375a(11) =9373a(12) =13176a(13) =18161a(14) =24402a(15) =32110a(16) =41472a(17) =52948a(18) =66339a(19) =82384a(20) =101100a(21) =122801a(22) =147741a(23) =176665a(24) =209088a(25) =246225a(26) =287976a(27) =334764a(28) =386904a(29) =445486