A320205 Number of sets of nonempty words with a total of n letters over quaternary alphabet such that all letters occur at least once in the set.

73, 976, 8416, 59488, 375698, 2209276, 12376430, 66974912, 353260192, 1827146732, 9306483104, 46822023764, 233203697318, 1151770103264, 5647971709608, 27525892585476, 133427763556914, 643682934370820, 3091947949892804, 14794516505019096, 70537743010768506

Offset: 4

Author

Alois P. Heinz, Oct 07 2018

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 4..1000

Crossrefs

Column k=4 of A319501.

Cf. A320214.

Programs

Maple

h:= proc(n, i, k) option remember; `if`(n=0, 1, `if`(i<1, 0,
      add(h(n-i*j, i-1, k)*binomial(k^i, j), j=0..n/i)))
    end:
a:= n-> (k-> add((-1)^i*binomial(k, i)*h(n$2, k-i), i=0..k))(4):
seq(a(n), n=4..30);