A132444 Number of n x n crossword puzzles with rotational symmetry and exactly one black square per row, up to symmetry.

0, 0, 0, 1, 1, 5, 6, 60, 93

Offset

3,6

Comments

Acceptable crossword puzzles must have all words of length 3 or more, at least one word in each row and each column and be connected. Since the puzzles counted in sequence A132443 come naturally in pairs (by reflective symmetry), the numbers in this sequence are obtained by dividing the corresponding numbers in A132443 by 2.

Links

Table of n, a(n) for n=3..11.

Example

a(6) = 1 because up to symmetry, the only 6 X 6 crossword puzzle with exactly one black square in each row (using 1's for black squares and 0's for white) is:
100000
100000
100000
000001
000001
000001

Maple

See the program for A132443

Crossrefs

Cf. A130578, A132443, A132445, A132446.

Sequence in context: A299243 A191557 A223530 * A111504 A041057 A041058

Adjacent sequences: A132441 A132442 A132443 * A132445 A132446 A132447

Keyword

nonn

Author

Marc Brodie (mbrodie(AT)wju.edu), Aug 21 2007

Status

approved