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 A207272 #7 Jul 22 2025 20:14:02 %S A207272 14,196,488,1910,5904,14184,38911,90670,211626,485438,1060958,2325765, %T A207272 4961769,10471731,21898109,45173720,92638142,188237183,379950333, %U A207272 762511989,1520880047,3019622080,5966608758,11740776248,23016781362 %N A207272 Number of 5Xn 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 1 1 and 1 0 1 vertically. %C A207272 Row 5 of A207269 %H A207272 R. H. Hardin, <a href="/A207272/b207272.txt">Table of n, a(n) for n = 1..210</a> %F A207272 Empirical: a(n) = 3*a(n-1) +5*a(n-2) -5*a(n-3) -55*a(n-4) +a(n-5) +157*a(n-6) +288*a(n-7) -314*a(n-8) -900*a(n-9) -707*a(n-10) +1753*a(n-11) +2735*a(n-12) +1215*a(n-13) -4934*a(n-14) -5958*a(n-15) -2633*a(n-16) +9212*a(n-17) +10737*a(n-18) +6641*a(n-19) -12602*a(n-20) -15845*a(n-21) -13377*a(n-22) +12402*a(n-23) +17826*a(n-24) +20087*a(n-25) -7531*a(n-26) -14262*a(n-27) -22705*a(n-28) +935*a(n-29) +6999*a(n-30) +19219*a(n-31) +3067*a(n-32) -409*a(n-33) -12003*a(n-34) -3358*a(n-35) -2604*a(n-36) +5460*a(n-37) +1873*a(n-38) +2447*a(n-39) -1779*a(n-40) -585*a(n-41) -1256*a(n-42) +396*a(n-43) +61*a(n-44) +422*a(n-45) -53*a(n-46) +23*a(n-47) -96*a(n-48) +3*a(n-49) -9*a(n-50) +14*a(n-51) +a(n-53) -a(n-54) %e A207272 Some solutions for n=4 %e A207272 ..1..0..0..1....1..1..0..0....1..1..1..1....0..0..1..0....0..1..0..0 %e A207272 ..0..0..1..0....1..1..1..1....1..1..1..1....0..1..0..0....0..1..0..1 %e A207272 ..0..1..0..0....0..1..0..0....1..0..1..0....1..0..0..1....1..1..0..0 %e A207272 ..1..0..0..1....0..1..0..0....1..0..1..0....0..0..1..0....0..1..0..0 %e A207272 ..0..0..1..0....0..0..1..0....0..1..0..1....0..1..0..0....0..0..1..0 %K A207272 nonn %O A207272 1,1 %A A207272 _R. H. Hardin_ Feb 16 2012