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

Terms

a(0) =0a(1) =0a(2) =2a(3) =7a(4) =18a(5) =36a(6) =64a(7) =103a(8) =156a(9) =224a(10) =310a(11) =415a(12) =542a(13) =692a(14) =868a(15) =1071a(16) =1304a(17) =1568a(18) =1866a(19) =2199a(20) =2570a(21) =2980a(22) =3432a(23) =3927a(24) =4468a(25) =5056a(26) =5694a(27) =6383a(28) =7126a(29) =7924