Number of 4-tuples (w,x,y,z) with all terms in {1,...,n} and w*x<=3*y*z.

Terms

a(0) =0a(1) =1a(2) =15a(3) =75a(4) =224a(5) =525a(6) =1077a(7) =1960a(8) =3299a(9) =5249a(10) =7939a(11) =11534a(12) =16285a(13) =22313a(14) =29890a(15) =39289a(16) =50713a(17) =64431a(18) =80854a(19) =100157a(20) =122747a(21) =148980a(22) =179165a(23) =213687a(24) =253113a(25) =297646a(26) =347806a(27) =404160a(28) =467027a(29) =536878