A211944 Number of distinct finite languages over 3-ary alphabet, whose minimum regular expression has reverse Polish length 2n-1.

5, 15, 85, 589, 4512, 37477, 328718, 2998039

Offset

1,1

Links

Table of n, a(n) for n=1..8.

Hermann Gruber, Jonathan Lee, and Jeffrey Shallit, Enumerating regular expressions and their languages, arXiv:1204.4982v1 [cs.FL], 2012.

Crossrefs

Sequence in context: A165625 A058820 A054363 * A336998 A276474 A362577

Adjacent sequences: A211941 A211942 A211943 * A211945 A211946 A211947

Keyword

nonn,hard

Author

Hermann Gruber, Apr 26 2012

Status

approved