Number of sets of nonempty words with a total of n letters over quaternary alphabet containing the fourth letter such that within each prefix of a word every letter of the alphabet is at least as frequent as the subsequent alphabet letter.
A293885
Number of sets of nonempty words with a total of n letters over quaternary alphabet containing the fourth letter such that within each prefix of a word every letter of the alphabet is at least as frequent as the subsequent alphabet letter.
Terms
- a(0) =1a(1) =5a(2) =25a(3) =102a(4) =410a(5) =1545a(6) =5784a(7) =21015a(8) =76248a(9) =272377a(10) =974208a(11) =3455177a(12) =12287351a(13) =43502174a(14) =154554897a(15) =547955950a(16) =1950335934a(17) =6937352521a(18) =24777223885a(19) =88515560121a(20) =317513893877
External references
- oeis: A293885