A240610 - OEIS

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.

%I #11 Aug 28 2014 08:19:24

%S 1,1,2,5,14,45,149,509,1756,6082,21246,74125,260940,917060,3251573,

%T 11514563,41115372,146687475,527318119,1894548198,6853413645,

%U 24782205276,90165044683,327958242274,1199475359682,4386106532923,16118279172044,59223681674225

%N 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.

%H Alois P. Heinz and Vaclav Kotesovec, <a href="/A240610/b240610.txt">Table of n, a(n) for n = 0..1000</a> (first 175 terms from Alois P. Heinz)

%H Vaclav Kotesovec, <a href="/A240610/a240610.txt">Recurrence (of order 6)</a>

%F a(n) ~ 8465 * 4^n / (18 * Pi * n^3). - _Vaclav Kotesovec_, Aug 28 2014

%Y Column k=4 of A240608.

%K nonn

%O 0,3

%A _Alois P. Heinz_, Apr 09 2014