Number of ternary words of length n in which all digits 0..2 occur in every 5 consecutive digits.

Terms

a(0) =1a(1) =3a(2) =9a(3) =27a(4) =81a(5) =150a(6) =366a(7) =870a(8) =2022a(9) =4686a(10) =10974a(11) =25614a(12) =59742a(13) =139398a(14) =325350a(15) =759198a(16) =1771590a(17) =4134126a(18) =9647262a(19) =22512342a(20) =52533750a(21) =122590422a(22) =286071414a(23) =667563054a(24) =1557794622a(25) =3635198310a(26) =8482932318a(27) =19795382454a(28) =46193598486a(29) =107795266974