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

Terms

a(0) =0a(1) =1a(2) =4a(3) =13a(4) =29a(5) =56a(6) =95a(7) =150a(8) =222a(9) =315a(10) =430a(11) =571a(12) =739a(13) =938a(14) =1169a(15) =1436a(16) =1740a(17) =2085a(18) =2472a(19) =2905a(20) =3385a(21) =3916a(22) =4499a(23) =5138a(24) =5834a(25) =6591a(26) =7410a(27) =8295a(28) =9247a(29) =10270