Number of n-length words w over a 9-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.
A240615
Number of n-length words w over a 9-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.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =5a(4) =14a(5) =46a(6) =165a(7) =651a(8) =2771a(9) =12638a(10) =61397a(11) =315507a(12) =1708420a(13) =9693168a(14) =57360909a(15) =352099643a(16) =2229930365a(17) =14494768448a(18) =96229497555a(19) =649761232948
External references
- oeis: A240615