A209185 Number of words, either empty or beginning with the first letter of the cyclic 6-ary alphabet, where each letter of the alphabet occurs n times and letters of neighboring word positions are equal or neighbors in the alphabet.

1, 2, 202, 53768, 19341130, 8151741752, 3795394507240, 1892725627422240, 992594962274742090, 540969426319412656280, 303934170379321788972952, 175019302819674622982714912, 102858166922334018149414066152, 61493440878115135100772134725088

Offset

0,2

Comments

The first and the last letters are considered neighbors in a cyclic alphabet. The words are not considered cyclic here.

a(n) is also the number of (6*n-1)-step walks on 6-dimensional cubic lattice from (1,0,...,0) to (n,n,...,n) with positive unit steps in all dimensions such that the indices of dimensions used in consecutive steps differ by less than 2 or are in the set {1,6}.

Links

Table of n, a(n) for n=0..13.

Crossrefs

Column k=6 of A208879.

Sequence in context: A180301 A203773 A349982 * A216608 A375842 A238819

Adjacent sequences: A209182 A209183 A209184 * A209186 A209187 A209188

Keyword

nonn,walk

Author

Alois P. Heinz, Mar 05 2012

Status

approved