A240610 Number of n-length words w over a 4-ary alphabet such that w is empty or a prefix z concatenated with letter a_i and i=1 or 0 < #(z,a_{i-1}) >= #(z,a_i), where #(z,a_i) counts the occurrences of the i-th letter in z.
1, 1, 2, 5, 14, 45, 149, 509, 1756, 6082, 21246, 74125, 260940, 917060, 3251573, 11514563, 41115372, 146687475, 527318119, 1894548198, 6853413645, 24782205276, 90165044683, 327958242274, 1199475359682, 4386106532923, 16118279172044, 59223681674225
Offset: 0
Keywords
Links
- Alois P. Heinz and Vaclav Kotesovec, Table of n, a(n) for n = 0..1000 (first 175 terms from Alois P. Heinz)
- Vaclav Kotesovec, Recurrence (of order 6)
Crossrefs
Column k=4 of A240608.
Formula
a(n) ~ 8465 * 4^n / (18 * Pi * n^3). - Vaclav Kotesovec, Aug 28 2014