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A325408
Number of (2n+1) X (2n+1) black-and-white mirror-symmetric grids that are legal for crossword puzzles.
3
1, 5, 35, 436, 11348, 650798, 78816939, 19500572516, 10050221059942, 10777659213636406, 24081651896803403442
OFFSET
1,2
COMMENTS
Rules: Every white square must be "checked" (in both a horizontal and vertical word), words must be at least 3 letters long, the whole grid must be symmetric under both left-right and top-bottom mirror symmetry, and the set of white squares must be connected.
CROSSREFS
There are many other OEIS sequences related to crossword puzzles: search for "crossword puzzle" (without the quotes).
Sequence in context: A059865 A376322 A247596 * A097492 A125802 A034217
KEYWORD
nonn,more
AUTHOR
Michael Kleber, Apr 23 2019
EXTENSIONS
a(11) added by Akshay Ravikumar, Jun 20 2019
STATUS
approved