Number of length n word structures with all distinct runs using at most 3 symbols.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =9a(5) =21a(6) =46a(7) =108a(8) =223a(9) =487a(10) =1028a(11) =2060a(12) =4327a(13) =8591a(14) =16818a(15) =33562a(16) =64441a(17) =122983a(18) =232378a(19) =443446a(20) =816371a(21) =1503517a(22) =2775372a(23) =5052186a(24) =9116047a(25) =16231929a(26) =29182198a(27) =51503788a(28) =91032821a(29) =158301653