Number of length n strings on the alphabet {0,1,2,3} with digit sum at most 4.

Terms

a(0) =1a(1) =4a(2) =13a(3) =32a(4) =66a(5) =121a(6) =204a(7) =323a(8) =487a(9) =706a(10) =991a(11) =1354a(12) =1808a(13) =2367a(14) =3046a(15) =3861a(16) =4829a(17) =5968a(18) =7297a(19) =8836a(20) =10606a(21) =12629a(22) =14928a(23) =17527a(24) =20451a(25) =23726a(26) =27379a(27) =31438a(28) =35932a(29) =40891