Automorphisms of subword-posets

In this paper the automorphism group of two posets, image and image is determined. image is the poset of DNA strands of length at most n, built up with k complement pairs of letters, and partially ordered by the subsequence relation. image is the set of all subsequences of the word image defined over the alphabet image, where image. The automorphism group of image was known already (see G. Burosch, H.-D.O.F. Gronau, J.-M. Laborde, The automorphism group of the subsequence poset image, Order 16 (2) (1999) 179–194 (2000)), here a short proof is presented as an illustration of the method used in the first part.