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A recurrence, a determinant formula, and generating functions are presented for enumerating words with restricted letters by adjacencies. The main theorem leads to reÿnements (with up to two additional parameters) of known results on compositions, polyominoes, and permutations. Among the examples considered are (1) the introduction of the ascent variation(More)
Based Based on on two two inversion inversion formulas formulas for for enumerating enumerating words words in in the the free free monoid monoid by by adjacencies, adjacencies, we we present present a a new new approach approach to to a a class class of of permutation permutation problems problems having having Eulerian-type Eulerian-type generating(More)
As motivation for our designs, first consider the identity 1=0 Next, imagine inserting an' bi in the /th term of the sum and replacing 2' by (a + b)n The result is the binomial theorem. Our objective here is to examine the effect of an analogous "pollination" of Vander-monde's identity (nt) (1) Guided by our binomial theorem example, we slip four letters(More)