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 A383256 #10 Apr 23 2025 17:02:34 %S A383256 1,1,7,343,125465,366908001,8698468668251,1708834003295306868, %T A383256 2810884261025802145414705,39088555382409783097546399456477, %U A383256 4626844513673581956954679383115038810744,4688191496359773864437279635019555242588548880831 %N A383256 Number of n X n matrices of nonnegative entries with all columns summing to n and no horizontally adjacent zeros. %H A383256 John Tyler Rascoe, <a href="/A383256/a383256.py.txt">Python program</a>. %e A383256 a(1) = 1: [1] %e A383256 a(2) = 7: [1,1] [1,0] [1,2] [0,1] [2,1] [0,2] [2,0] %e A383256 [1,1], [1,2], [1,0], [2,1], [0,1], [2,0], [0,2]. %o A383256 (Python) %o A383256 # see links %Y A383256 Cf. A008300, A120733, A145839, A261780, A382923. %K A383256 nonn %O A383256 0,3 %A A383256 _John Tyler Rascoe_, Apr 21 2025 %E A383256 a(10)-a(11) from _Bert Dobbelaere_, Apr 23 2025