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 A208396 #7 Jul 22 2025 21:19:32 %S A208396 41,9842,2056392,438083928,93120350760,19798894881900, %T A208396 4209452449879284,894976200467603100,190281795998287100868, %U A208396 40456006404952930502220,8601392693737014451368372,1828750854693797651745630540 %N A208396 Number of 5Xn 0..2 arrays with new values 0..2 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 A208396 Row 5 of A208392 %H A208396 R. H. Hardin, <a href="/A208396/b208396.txt">Table of n, a(n) for n = 1..210</a> %F A208396 Empirical: a(n) = 171*a(n-1) +8504*a(n-2) +77860*a(n-3) -1000900*a(n-4) -11005932*a(n-5) +78914544*a(n-6) +374284064*a(n-7) -3897108352*a(n-8) +9817487872*a(n-9) -6449426432*a(n-10) -6696632320*a(n-11) +7534936064*a(n-12) +1817837568*a(n-13) -2092433408*a(n-14) -484442112*a(n-15) for n>18 %e A208396 Some solutions for n=4 %e A208396 ..0..0..0..0....0..0..0..0....0..0..1..1....0..1..0..2....0..1..0..2 %e A208396 ..0..1..2..1....1..0..1..0....1..1..2..0....1..1..1..2....1..2..2..1 %e A208396 ..0..0..2..0....2..1..0..0....1..2..1..2....1..2..2..1....1..0..1..1 %e A208396 ..0..2..1..2....2..0..1..0....0..1..2..1....1..1..0..1....0..0..2..0 %e A208396 ..1..1..1..1....2..0..0..1....2..0..0..1....2..2..1..2....0..2..0..0 %K A208396 nonn %O A208396 1,1 %A A208396 _R. H. Hardin_ Feb 25 2012