Number of sets of nonempty words with a total of n letters over quaternary alphabet such that within each prefix of a word every letter of the alphabet is at least as frequent as the subsequent alphabet letter.
A293743
Number of sets of nonempty words with a total of n letters over quaternary alphabet 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) =1a(2) =2a(3) =6a(4) =15a(5) =44a(6) =129a(7) =386a(8) =1185a(9) =3690a(10) =11725a(11) =37578a(12) =122577a(13) =402477a(14) =1340640a(15) =4490368a(16) =15219148a(17) =51825464a(18) =178235039a(19) =615461671a(20) =2143127872a(21) =7488890027a(22) =26357539204a(23) =93050275129a(24) =330544091758
External references
- oeis: A293743