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.
%I A215875 #7 Jul 22 2025 23:26:53 %S A215875 1,1,1,8,100,2988,97289,6812794,386699176,48337803306 %N A215875 Number of permutations of 0..floor((7*n-2)/2) on odd squares of an 7Xn array such that each row, column, diagonal and (downwards) antidiagonal of odd squares is increasing. %C A215875 Row 7 of A215870 %e A215875 Some solutions for n=4 %e A215875 ..x..0..x..1....x..0..x..1....x..0..x..1....x..0..x..2....x..0..x..2 %e A215875 ..2..x..3..x....2..x..3..x....2..x..3..x....1..x..3..x....1..x..3..x %e A215875 ..x..4..x..5....x..4..x..5....x..4..x..6....x..4..x..6....x..4..x..5 %e A215875 ..6..x..7..x....6..x..7..x....5..x..7..x....5..x..7..x....6..x..7..x %e A215875 ..x..8..x..9....x..8..x.10....x..8..x..9....x..8..x.10....x..8..x..9 %e A215875 .10..x.11..x....9..x.11..x...10..x.11..x....9..x.11..x...10..x.11..x %e A215875 ..x.12..x.13....x.12..x.13....x.12..x.13....x.12..x.13....x.12..x.13 %K A215875 nonn %O A215875 1,4 %A A215875 _R. H. Hardin_ Aug 25 2012