a(n) = number of n-lettered words in the alphabet {1, 2, 3} with as many occurrences of the substring (consecutive subword) [1, 2] as of [1, 3].

A211279

a(n) = number of n-lettered words in the alphabet {1, 2, 3} with as many occurrences of the substring (consecutive subword) [1, 2] as of [1, 3].

Terms

    a(0) =1a(1) =3a(2) =7a(3) =15a(4) =33a(5) =81a(6) =223a(7) =651a(8) =1915a(9) =5559a(10) =15921a(11) =45333a(12) =129309a(13) =371025a(14) =1071411a(15) =3108951a(16) =9047853a(17) =26374005a(18) =76959295a(19) =224790195a(20) =657326803a(21) =1924486719a(22) =5641225341a(23) =16554458025a(24) =48627650779a(25) =142963972275a(26) =420635073625

External references