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

Terms

a(0) =0a(1) =0a(2) =4a(3) =18a(4) =54a(5) =129a(6) =262a(7) =478a(8) =807a(9) =1281a(10) =1938a(11) =2821a(12) =3975a(13) =5451a(14) =7305a(15) =9595a(16) =12385a(17) =15744a(18) =19743a(19) =24459a(20) =29974a(21) =36372a(22) =43743a(23) =52182a(24) =61786a(25) =72658a(26) =84906a(27) =98640a(28) =113976a(29) =131035