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A180439 a(n) counts the distinct cubical (on alphabet of 3 symbols) billiard words with length n, acting as prefix to just k = 3 such words of length n+1 (that is, a subset of "special"). 2
1, 3, 3, 3, 9, 15, 33, 63, 153, 219, 261, 351, 585, 879, 933, 1233, 1401, 1899, 2301, 3111 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
By symmetry under reversal, a(n) also counts length n cubical billiard words acting as suffix to just k length n+1 cubical billiard words. Computation: Fred Lunnon for 0 <= n <= 19 (Magma). The program in A180437 counts k-special words for k = 1,...,m, where m = 3 denotes the size of the alphabet.
LINKS
CROSSREFS
Sequence in context: A217457 A231753 A231663 * A298315 A299189 A231651
KEYWORD
nonn,more
AUTHOR
Fred Lunnon, Sep 05 2010
STATUS
approved

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Last modified March 29 05:28 EDT 2024. Contains 371264 sequences. (Running on oeis4.)