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

Terms

a(0) =0a(1) =0a(2) =11a(3) =69a(4) =231a(5) =584a(6) =1230a(7) =2307a(8) =3964a(9) =6385a(10) =9771a(11) =14356a(12) =20377a(13) =28125a(14) =37894a(15) =50008a(16) =64809a(17) =82681a(18) =104005a(19) =129216a(20) =158743a(21) =193063a(22) =232668a(23) =278080a(24) =329812a(25) =388452a(26) =454585a(27) =528822a(28) =611791a(29) =704167