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 A208407 #7 Jul 22 2025 21:20:10 %S A208407 715,10370330,157873031498,2403711876698218,36598079445605633928, %T A208407 557229580446475130201608,8484183047877022205116428184, %U A208407 129177209027669581083328287797640,1966807085374417176424317546443585928 %N A208407 Number of nX7 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than two of its immediate leftward or upward or right-upward antidiagonal neighbors. %C A208407 Column 7 of A208408 %H A208407 R. H. Hardin, <a href="/A208407/b208407.txt">Table of n, a(n) for n = 1..210</a> %e A208407 Some solutions for n=4 %e A208407 ..0..0..0..0..1..2..1....0..0..0..1..0..0..0....0..0..0..0..0..0..0 %e A208407 ..1..1..0..2..1..3..3....1..0..2..2..1..1..2....0..1..0..1..0..2..1 %e A208407 ..1..2..0..2..2..1..2....2..0..1..3..1..3..1....0..2..2..3..0..0..1 %e A208407 ..0..0..1..0..2..2..0....0..3..3..3..2..1..3....0..3..3..3..3..1..3 %K A208407 nonn %O A208407 1,1 %A A208407 _R. H. Hardin_ Feb 26 2012