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) =63a(4) =180a(5) =437a(6) =891a(7) =1628a(8) =2736a(9) =4392a(10) =6600a(11) =9646a(12) =13608a(13) =18669a(14) =24990a(15) =32955a(16) =42432a(17) =54033a(18) =67797a(19) =84010a(20) =102900a(21) =125118a(22) =150282a(23) =179444a(24) =212544a(25) =249977a(26) =292032a(27) =339687a(28) =392196a(29) =451165