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) =0a(3) =6a(4) =20a(5) =58a(6) =124a(7) =244a(8) =424a(9) =700a(10) =1080a(11) =1610a(12) =2300a(13) =3206a(14) =4340a(15) =5768a(16) =7504a(17) =9624a(18) =12144a(19) =15150a(20) =18660a(21) =22770a(22) =27500a(23) =32956a(24) =39160a(25) =46228a(26) =54184a(27) =63154a(28) =73164a(29) =84350