Number of words of length 4n such that all letters of the n-ary 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.
A258499
Number of words of length 4n such that all letters of the n-ary 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) =1a(1) =1a(2) =34a(3) =3509a(4) =657370a(5) =182587701a(6) =67773956250
External references
- oeis: A258499