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 A208413 #7 Jul 22 2025 21:20:23 %S A208413 187,700075,2646531062,10084768380770,38410047476679936, %T A208413 146298576850884166522,557229580446475130201608, %U A208413 2122405243795588131572978866,8083928267793741312454314127058 %N A208413 Number of 6Xn 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 A208413 Row 6 of A208408 %H A208413 R. H. Hardin, <a href="/A208413/b208413.txt">Table of n, a(n) for n = 1..210</a> %e A208413 Some solutions for n=4 %e A208413 ..0..1..0..0....0..0..0..0....0..0..0..0....0..0..0..1....0..0..0..0 %e A208413 ..1..0..1..0....0..1..0..1....1..1..2..1....1..2..2..0....1..1..2..0 %e A208413 ..2..3..1..3....2..1..3..2....1..2..1..3....1..3..1..3....2..2..1..0 %e A208413 ..2..2..1..1....1..3..0..3....2..3..1..0....1..0..3..3....3..2..2..0 %e A208413 ..3..2..0..1....1..0..2..1....0..1..1..1....3..2..1..3....2..3..3..0 %e A208413 ..0..3..3..1....0..3..3..3....1..2..2..3....2..2..2..2....1..2..3..2 %K A208413 nonn %O A208413 1,1 %A A208413 _R. H. Hardin_ Feb 26 2012