Number of n-length ternary words avoiding runs of zeros of length 1 (mod 3).

Terms

a(0) =1a(1) =2a(2) =5a(3) =13a(4) =32a(5) =79a(6) =197a(7) =490a(8) =1217a(9) =3025a(10) =7520a(11) =18691a(12) =46457a(13) =115474a(14) =287021a(15) =713413a(16) =1773248a(17) =4407559a(18) =10955357a(19) =27230458a(20) =67683593a(21) =168233257a(22) =418157888a(23) =1039366555a(24) =2583432881a(25) =6421339426a(26) =15960778517a(27) =39671855677a(28) =98607729632