Number of (w,x,y,z) with all terms in {1,...,n} and 3w=x+y+z+n+2.

Terms

a(0) =0a(1) =0a(2) =0a(3) =3a(4) =11a(5) =24a(6) =45a(7) =76a(8) =117a(9) =171a(10) =240a(11) =324a(12) =426a(13) =548a(14) =690a(15) =855a(16) =1045a(17) =1260a(18) =1503a(19) =1776a(20) =2079a(21) =2415a(22) =2786a(23) =3192a(24) =3636a(25) =4120a(26) =4644a(27) =5211a(28) =5823a(29) =6480