A293884 Number of sets of nonempty words with a total of n letters over ternary alphabet containing the third letter such that within each prefix of a word every letter of the alphabet is at least as frequent as the subsequent alphabet letter.

1, 4, 16, 53, 173, 532, 1615, 4785, 14066, 40908, 118438, 341253, 981200, 2815762, 8075265, 23149097, 66373778, 190376443, 546401592, 1569387414, 4511532695, 12980998062, 37385342522, 107771434819, 310967929569, 898108427259, 2596180252466, 7511411442182

Offset: 3

Author

Alois P. Heinz, Oct 18 2017

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 3..1000

Crossrefs

Column k=3 of A293113.

Cf. A293741, A293742.

Formula

a(n) = A293742(n) - A293741(n).