Number of strings of length n over a 4-letter alphabet that do not begin with a palindrome.

A252697

Number of strings of length n over a 4-letter alphabet that do not begin with a palindrome.

Terms

    a(0) =0a(1) =4a(2) =12a(3) =36a(4) =132a(5) =492a(6) =1932a(7) =7596a(8) =30252a(9) =120516a(10) =481572a(11) =1924356a(12) =7695492a(13) =30774372a(14) =123089892a(15) =492329316a(16) =1969287012a(17) =7877027532a(18) =31507989612a(19) =126031476876a(20) =504125425932

External references