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

Terms

a(0) =0a(1) =0a(2) =5a(3) =31a(4) =106a(5) =270a(6) =575a(7) =1085a(8) =1876a(9) =3036a(10) =4665a(11) =6875a(12) =9790a(13) =13546a(14) =18291a(15) =24185a(16) =31400a(17) =40120a(18) =50541a(19) =62871a(20) =77330a(21) =94150a(22) =113575a(23) =135861a(24) =161276a(25) =190100a(26) =222625a(27) =259155a(28) =300006a(29) =345506