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.
A386254
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.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =6a(4) =18a(5) =60a(6) =240a(7) =1085a(8) =5012a(9) =23730a(10) =121440a(11) =685707a(12) =4144668a(13) =25614589a(14) =159141892a(15) =1012740885a(16) =6805631232a(17) =48872707006a(18) =369227821608
External references
- oeis: A386254