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

Terms

a(0) =0a(1) =0a(2) =1a(3) =6a(4) =15a(5) =30a(6) =54a(7) =87a(8) =131a(9) =189a(10) =261a(11) =349a(12) =456a(13) =582a(14) =729a(15) =900a(16) =1095a(17) =1316a(18) =1566a(19) =1845a(20) =2155a(21) =2499a(22) =2877a(23) =3291a(24) =3744a(25) =4236a(26) =4769a(27) =5346a(28) =5967a(29) =6634