Number of (w,x,y,z) with all terms in {1,...,n} and w<2x and y>=3z.

Terms

a(0) =0a(1) =0a(2) =0a(3) =7a(4) =24a(5) =57a(6) =135a(7) =259a(8) =432a(9) =732a(10) =1125a(11) =1638a(12) =2376a(13) =3302a(14) =4410a(15) =5915a(16) =7680a(17) =9765a(18) =12393a(19) =15447a(20) =18900a(21) =23170a(22) =27951a(23) =33348a(24) =39744a(25) =46900a(26) =54756a(27) =63999a(28) =74088a(29) =85185