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

Terms

a(0) =0a(1) =1a(2) =15a(3) =73a(4) =228a(5) =551a(6) =1137a(7) =2097a(8) =3568a(9) =5701a(10) =8675a(11) =12681a(12) =17940a(13) =24683a(14) =33173a(15) =43681a(16) =56512a(17) =71977a(18) =90423a(19) =112201a(20) =137700a(21) =167311a(22) =201465a(23) =240593a(24) =285168a(25) =335661a(26) =392587a(27) =456457a(28) =527828a(29) =607251