Number of words of length n over an infinite alphabet such that all prefixes satisfy c(3*k + 1) >= c(3*k + 2), c(3*k + 1) >= c(3*k), c(3*k + 2) >= c(3*j + 1), and c(3*k) >= c(3*j + 1) for 0 <= k < j, where c(i) is the number of occurrences of the letter i.
A392551
Number of words of length n over an infinite alphabet such that all prefixes satisfy c(3*k + 1) >= c(3*k + 2), c(3*k + 1) >= c(3*k), c(3*k + 2) >= c(3*j + 1), and c(3*k) >= c(3*j + 1) for 0 <= k < j, where c(i) is the number of occurrences of the letter i.
Terms
- a(0) =1a(1) =1a(2) =3a(3) =7a(4) =19a(5) =59a(6) =201a(7) =735a(8) =2865a(9) =11565a(10) =49173a(11) =217205a(12) =989073a(13) =4671751a(14) =22833321a(15) =115197047a(16) =600039917a(17) =3217059631a(18) =17717906301a(19) =100031568989a(20) =577538335491
External references
- oeis: A392551