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 A368809 #39 Feb 05 2025 09:20:21 %S A368809 1,41,1041,22193,433801,8057625,144762849,2540882465,43840779353, %T A368809 746649798473,12587443678705,210491254232465,3496816762316713, %U A368809 57778098654714361,950391251581267073,15574198350636963201,254405750326548970361,4144508602760970898729,67361936661916258817937 %N A368809 Number of 4 X n binary arrays with a path of adjacent 1's from top row to bottom row using only left, right, and downward steps. %C A368809 Unlike A069362, does not allow upward steps. %H A368809 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (36,-413,1642,-2536,1152). %F A368809 G.f.: x*(1 + 5*x - 22*x^2 + 8*x^3)/((1 - 16*x)*(1 - 20*x + 93*x^2 - 154*x^3 + 72*x^4)). - _Pontus von Brömssen_, Feb 05 2025 %e A368809 For example, here is one such 4 X 4 array: %e A368809 0001 %e A368809 1111 %e A368809 1010 %e A368809 1100 %e A368809 The following 4 X 5 array is a non-example, as there is no path using only left, right, and downward steps: %e A368809 10000 %e A368809 10111 %e A368809 11101 %e A368809 00001 %Y A368809 Row 4 of A369892. %Y A368809 Cf. A069362, A359576. %K A368809 nonn,easy %O A368809 1,2 %A A368809 _Caleb Stanford_, Feb 05 2024 %E A368809 More terms from _Pontus von Brömssen_, Feb 05 2025