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 A213798 #6 Jul 22 2025 23:04:30 %S A213798 1,7,153,23753,22698959,138198204339 %N A213798 Number of n X n 0..6 symmetric arrays with every row summing to 3*n. %C A213798 Column 6 of A213800 %e A213798 Some solutions for n=4 %e A213798 ..3..1..2..6....0..0..6..6....0..3..3..6....6..6..0..0....3..5..1..3 %e A213798 ..1..5..2..4....0..5..1..6....3..4..4..1....6..2..3..1....5..6..0..1 %e A213798 ..2..2..6..2....6..1..5..0....3..4..1..4....0..3..3..6....1..0..5..6 %e A213798 ..6..4..2..0....6..6..0..0....6..1..4..1....0..1..6..5....3..1..6..2 %K A213798 nonn %O A213798 1,2 %A A213798 _R. H. Hardin_ Jun 20 2012