a(n) counts the distinct cubical (on alphabet of 3 symbols) billiard words with length n, acting as prefix to just k = 1 such word of length n+1 (that is, not "special").
A180437
a(n) counts the distinct cubical (on alphabet of 3 symbols) billiard words with length n, acting as prefix to just k = 1 such word of length n+1 (that is, not "special").
Terms
- a(0) =0a(1) =0a(2) =0a(3) =6a(4) =24a(5) =78a(6) =186a(7) =372a(8) =876a(9) =1632a(10) =3024a(11) =5310a(12) =8496a(13) =13344a(14) =21186a(15) =31878a(16) =46752a(17) =66936a(18) =94800a(19) =130194
External references
- oeis: A180437