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 A067211 #20 Jun 28 2025 22:12:22 %S A067211 1,4,16,340,89520,290838284,12092687195284,6675338514190905402, %T A067211 50327836869668591230004816,5292118931181847999077738163123240, %U A067211 7888144623867099277720906683959732404332016,168815361056027801755263418243053345902341535059333028 %N A067211 Number of n X n 0..3 matrices with all row and column sums equal. %e A067211 Some solutions for n=3 %e A067211 ..2..1..1....1..3..1....0..2..1....2..2..2....0..0..3....1..2..1....1..3..3 %e A067211 ..0..1..3....1..1..3....3..0..0....2..2..2....2..1..0....0..1..3....3..1..3 %e A067211 ..2..2..0....3..1..1....0..1..2....2..2..2....1..2..0....3..1..0....3..3..1 %Y A067211 Column k=3 of A202784. %K A067211 nonn %O A067211 0,2 %A A067211 _R. H. Hardin_, Feb 20 2002 %E A067211 Added one term and example - _R. H. Hardin_, Jan 05 2012 %E A067211 a(7)-a(10) from _Andrew Howroyd_, Jun 01 2017 %E A067211 a(11) from _Sean A. Irvine_, Dec 14 2023 %E A067211 a(0)=1 prepended by _Andrew Howroyd_, Oct 14 2024