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 (4*n-1)-step walks on 4-dimensional cubic lattice from (1,0,0,0) to (n,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 {1,4}.
CROSSREFS
KEYWORD
nonn,walk
AUTHOR
Alois P. Heinz, Mar 05 2012
STATUS
approved