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

Terms

a(0) =0a(1) =0a(2) =4a(3) =14a(4) =44a(5) =98a(6) =200a(7) =356a(8) =600a(9) =940a(10) =1420a(11) =2050a(12) =2884a(13) =3934a(14) =5264a(15) =6888a(16) =8880a(17) =11256a(18) =14100a(19) =17430a(20) =21340a(21) =25850a(22) =31064a(23) =37004a(24) =43784a(25) =51428a(26) =60060a(27) =69706a(28) =80500a(29) =92470