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

Terms

a(0) =0a(1) =1a(2) =12a(3) =67a(4) =212a(5) =527a(6) =1096a(7) =2045a(8) =3496a(9) =5621a(10) =8580a(11) =12591a(12) =17852a(13) =24627a(14) =33152a(15) =43737a(16) =56656a(17) =72265a(18) =90876a(19) =112891a(20) =138660a(21) =168631a(22) =203192a(23) =242837a(24) =287992a(25) =339197a(26) =396916a(27) =461735a(28) =534156a(29) =614811