The operation shortens each run of consecutive equal terms by one term (runs of length 1 vanish).
Table of n, a(n) for n=1..41.
Claude Lenormand, Deux transformations sur les mots, Preprint, 5 pages, Nov 17 2003. Apparently unpublished. This is a scanned copy of the version that the author sent to me in 2003.
Cf. A306211, A318921.
Sequence in context: A271518 A106825 A156608 * A275850 A112505 A104638
Adjacent sequences: A323824 A323825 A323826 * A323828 A323829 A323830
N. J. A. Sloane, Feb 01 2019