a(n) counts the distinct cubical (on alphabet of 3 symbols) billiard words with length n, acting as prefix to just k = 2 such words of length n+1 (that is, a subset of "special").
A180438
a(n) counts the distinct cubical (on alphabet of 3 symbols) billiard words with length n, acting as prefix to just k = 2 such words of length n+1 (that is, a subset of "special").
Terms
- a(0) =0a(1) =0a(2) =6a(3) =18a(4) =36a(5) =78a(6) =150a(7) =306a(8) =420a(9) =792a(10) =1338a(11) =2082a(12) =3228a(13) =4830a(14) =7050a(15) =9954a(16) =13920a(17) =18738a(18) =24666a(19) =32610
External references
- oeis: A180438