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 A208074 #7 Jul 22 2025 21:09:10 %S A208074 10,100,510,2601,16065,99225,572040,3297856,19523816,115584001, %T A208074 677087229,3966354441,23333593542,137268768004,806149925790, %U A208074 4734344981025,27823208376315,163513839286009,960678492827472,5644189938974976 %N A208074 Number of nX4 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 0 0 and 0 1 0 vertically. %C A208074 Column 4 of A208078 %H A208074 R. H. Hardin, <a href="/A208074/b208074.txt">Table of n, a(n) for n = 1..210</a> %F A208074 Empirical: a(n) = 2*a(n-1) -6*a(n-2) +68*a(n-3) +423*a(n-4) +628*a(n-5) +3408*a(n-6) -1012*a(n-7) -25184*a(n-8) -35190*a(n-9) -153252*a(n-10) -83452*a(n-11) +428108*a(n-12) +439718*a(n-13) +2263840*a(n-14) +1738832*a(n-15) -2514276*a(n-16) -833180*a(n-17) -13759668*a(n-18) -9299992*a(n-19) +5925976*a(n-20) -4763970*a(n-21) +39538848*a(n-22) +18089492*a(n-23) -3827918*a(n-24) +16850326*a(n-25) -54844740*a(n-26) -11657172*a(n-27) -4162646*a(n-28) -14808148*a(n-29) +34708980*a(n-30) +2471388*a(n-31) +4632424*a(n-32) +5367702*a(n-33) -10574840*a(n-34) +162700*a(n-35) -1570596*a(n-36) -839990*a(n-37) +1515040*a(n-38) -110280*a(n-39) +231228*a(n-40) +46604*a(n-41) -89320*a(n-42) +9032*a(n-43) -14064*a(n-44) -526*a(n-45) +1796*a(n-46) -180*a(n-47) +287*a(n-48) -8*a(n-49) -6*a(n-50) -a(n-52) %e A208074 Some solutions for n=4 %e A208074 ..1..0..1..1....1..1..1..0....0..1..0..0....1..0..1..0....1..0..1..0 %e A208074 ..1..0..1..0....0..1..1..1....0..1..0..1....0..1..0..0....1..1..0..1 %e A208074 ..1..1..0..0....1..1..0..1....1..0..1..1....1..1..1..1....0..1..1..1 %e A208074 ..0..1..1..1....1..0..1..0....1..0..1..0....1..1..1..1....1..1..1..1 %K A208074 nonn %O A208074 1,1 %A A208074 _R. H. Hardin_ Feb 23 2012