A323839 Number of (2n+1) X (2n+1) black-and-white grids that are legal for crossword puzzles and have no all-black edges.

1, 12, 312, 31187, 17438702, 40575832476, 404139015237875, 17253201646564115439, 3185118492387669085270268, 2540927098290913247876202007100

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 180-degree rotation, and the set of white squares must be connected.

Computed by Michael Kleber.

References

Michael Kleber, Posting to Math Fun Mailing List, Feb 04 2019.

Links

Table of n, a(n) for n=1..10.

Crossrefs

Cf. A323838, A325408, A325409

There are many other OEIS sequences related to crossword puzzles: search for "crossword puzzle" (without the quotes).

Sequence in context: A171094 A060010 A129583 * A163585 A341185 A279293

Adjacent sequences: A323836 A323837 A323838 * A323840 A323841 A323842

Keyword

nonn,more

Author

N. J. A. Sloane, Feb 04 2019

Extensions

a(4)-a(7) corrected by Michael Kleber, Feb 06 2019

a(8)-a(10) added by Michael Kleber, Apr 23 2019

Status

approved