Number of words of length n over an infinite alphabet such that for any letter k appearing within a word the letter k appears at least k times and exactly one of each kind of letter is marked.
A386255
Number of words of length n over an infinite alphabet such that for any letter k appearing within a word the letter k appears at least k times and exactly one of each kind of letter is marked.
Terms
- a(0) =1a(1) =1a(2) =4a(3) =15a(4) =64a(5) =325a(6) =1776a(7) =11179a(8) =72640a(9) =489969a(10) =3435580a(11) =26495491a(12) =221599104a(13) =1893705697a(14) =16145571820a(15) =138299146665
External references
- oeis: A386255