This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
a(6) = 2 because the only two 6 X 6 crossword puzzles are (using 1's for black squares and 0's for white): 100000 100000 100000 000001 000001 000001 and 000001 000001 000001 100000 100000 100000
a(5) = 5 because the only acceptable 5 X 5 crossword puzzles are (using 1's for black squares and 0's for white) are: 00000 10000 10000 00001 00001 00000 00000 10000 00000 00001 00000 00000 00000 00000 00000 00000 00000 00001 00000 10000 00000 00001 00001 10000 10000
a(5) = 3 because up to symmetry the only 5 x 5 acceptable crossword puzzles with at most one black square per row (using 1's for black squares and 0's for white) are: 00000 10000 10000 00000 00000 10000 00000 00000 00000 00000 00000 00001 00000 00001 00001
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