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%I #12 Jun 22 2019 00:45:35
%S 1,5,35,436,11348,650798,78816939,19500572516,10050221059942,
%T 10777659213636406,24081651896803403442
%N Number of (2n+1) X (2n+1) black-and-white mirror-symmetric grids that are legal for crossword puzzles.
%C 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.
%Y Cf. A323838, A323839, A325409.
%Y There are many other OEIS sequences related to crossword puzzles: search for "crossword puzzle" (without the quotes).
%K nonn,more
%O 1,2
%A _Michael Kleber_, Apr 23 2019
%E a(11) added by _Akshay Ravikumar_, Jun 20 2019