Length of longest legal domino snake using full set of dominoes up to [n:n].

Terms

a(0) =1a(1) =3a(2) =6a(3) =9a(4) =15a(5) =19a(6) =28a(7) =33a(8) =45a(9) =51a(10) =66a(11) =73a(12) =91a(13) =99a(14) =120a(15) =129a(16) =153a(17) =163a(18) =190a(19) =201a(20) =231a(21) =243a(22) =276a(23) =289a(24) =325a(25) =339a(26) =378a(27) =393a(28) =435a(29) =451