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 A183324 #10 Jul 22 2025 08:49:38 %S A183324 1,3,6,10,19,37,69,129,244,460,865,1629,3069,5779,10882,20494,38595, %T A183324 72681,136873,257761,485416,914136,1721505,3241945,6105241,11497411, %U A183324 21651966,40775058,76787731,144606925,272324269,512842017,965785884 %N A183324 Number of nX3 binary arrays with each 1 adjacent to exactly two other 1s. %C A183324 Column 3 of A183328 %H A183324 R. H. Hardin, <a href="/A183324/b183324.txt">Table of n, a(n) for n = 1..200</a> %F A183324 Empirical: a(n)=2*a(n-1)-a(n-2)+2*a(n-3)-a(n-4). %F A183324 Empirical: G.f. -x*(-1-x+x^3-x^2) / ( 1-2*x+x^2-2*x^3+x^4 ), see A033305 - _R. J. Mathar_, Sep 27 2013 %e A183324 All solutions for 4X3 %e A183324 ..0..0..0....0..0..0....1..1..1....0..0..0....0..0..0....0..0..0....1..1..0 %e A183324 ..0..0..0....0..0..0....1..0..1....1..1..1....0..1..1....1..1..0....1..1..0 %e A183324 ..1..1..0....0..0..0....1..0..1....1..0..1....0..1..1....1..1..0....0..0..0 %e A183324 ..1..1..0....0..0..0....1..1..1....1..1..1....0..0..0....0..0..0....0..0..0 %e A183324 ... %e A183324 ..0..0..0....0..1..1....1..1..1 %e A183324 ..0..0..0....0..1..1....1..0..1 %e A183324 ..0..1..1....0..0..0....1..1..1 %e A183324 ..0..1..1....0..0..0....0..0..0 %K A183324 nonn %O A183324 1,2 %A A183324 _R. H. Hardin_ Jan 03 2011