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) =8a(4) =24a(5) =40a(6) =76a(7) =112a(8) =176a(9) =240a(10) =340a(11) =440a(12) =584a(13) =728a(14) =924a(15) =1120a(16) =1376a(17) =1632a(18) =1956a(19) =2280a(20) =2680a(21) =3080a(22) =3564a(23) =4048a(24) =4624a(25) =5200a(26) =5876a(27) =6552a(28) =7336a(29) =8120