Number of words of length 2n such that all letters of the ternary alphabet occur at least once and are introduced in ascending order and which can be built by repeatedly inserting doublets into the initially empty word.

A258490

Number of words of length 2n such that all letters of the ternary alphabet occur at least once and are introduced in ascending order and which can be built by repeatedly inserting doublets into the initially empty word.

Terms

    a(0) =5a(1) =56a(2) =465a(3) =3509a(4) =25571a(5) =184232a(6) =1325609a(7) =9567545a(8) =69387483a(9) =505915981a(10) =3708195075a(11) =27314663271a(12) =202116910415

External references