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 A207753 #8 Jun 25 2018 12:46:47 %S A207753 9,81,270,900,2100,4900,9450,18225,31185,53361,84084,132496,196560, %T A207753 291600,413100,585225,799425,1092025,1448370,1920996,2486484,3218436, %U A207753 4081350,5175625,6449625,8037225,9865800,12110400,14671680,17774656 %N A207753 Number of 4 X n 0..1 arrays avoiding 0 0 1 and 0 1 1 horizontally and 0 0 1 and 1 0 0 vertically. %C A207753 Row 4 of A207752. %H A207753 R. H. Hardin, <a href="/A207753/b207753.txt">Table of n, a(n) for n = 1..210</a> %F A207753 Empirical: a(n) = 2*a(n-1) + 4*a(n-2) - 10*a(n-3) - 5*a(n-4) + 20*a(n-5) - 20*a(n-7) + 5*a(n-8) + 10*a(n-9) - 4*a(n-10) - 2*a(n-11) + a(n-12). %F A207753 Empirical g.f.: x*(9 + 63*x + 72*x^2 + 126*x^3 + 75*x^4 + 25*x^5 - 20*x^6 + 5*x^7 + 10*x^8 - 4*x^9 - 2*x^10 + x^11) / ((1 - x)^7*(1 + x)^5). - _Colin Barker_, Jun 25 2018 %e A207753 Some solutions for n=4: %e A207753 ..1..0..0..0....1..1..0..1....0..0..0..0....1..0..1..0....1..1..1..1 %e A207753 ..0..0..0..0....0..0..0..0....1..1..1..1....0..0..0..0....0..0..0..0 %e A207753 ..1..0..0..0....1..1..0..1....0..1..0..1....1..0..1..0....1..1..1..1 %e A207753 ..0..0..0..0....1..0..0..0....1..1..1..0....1..0..1..0....0..0..0..0 %Y A207753 Cf. A207752. %K A207753 nonn %O A207753 1,1 %A A207753 _R. H. Hardin_, Feb 19 2012