Number of (w,x,y,z) with all terms in {0,...,n} and w=2*floor((x+y+z)/2).

Terms

a(0) =1a(1) =4a(2) =17a(3) =20a(4) =53a(5) =56a(6) =117a(7) =120a(8) =217a(9) =220a(10) =361a(11) =364a(12) =557a(13) =560a(14) =813a(15) =816a(16) =1137a(17) =1140a(18) =1537a(19) =1540a(20) =2021a(21) =2024a(22) =2597a(23) =2600a(24) =3273a(25) =3276a(26) =4057a(27) =4060a(28) =4957a(29) =4960