Number of ternary codes of length 4 with n words.

Terms

a(0) =1a(1) =1a(2) =4a(3) =20a(4) =144a(5) =1245a(6) =12473a(7) =120213a(8) =1067757a(9) =8508432a(10) =60801152a(11) =391078610a(12) =2277606189a(13) =12079172109a(14) =58646808981a(15) =261900799332