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 A224009 #6 Jul 23 2025 04:50:31 %S A224009 21,441,6815,90051,1108969,13275381,157347899,1859567103,21962353421, %T A224009 259365424097,3063049674271,36174616727819,427225636505145, %U A224009 5045588330345405,59589072289828011,703755006991845799 %N A224009 Number of nX5 0..2 arrays with rows nondecreasing and antidiagonals unimodal. %C A224009 Column 5 of A224012 %H A224009 R. H. Hardin, <a href="/A224009/b224009.txt">Table of n, a(n) for n = 1..210</a> %F A224009 Empirical: a(n) = 21*a(n-1) -141*a(n-2) +427*a(n-3) -546*a(n-4) +526*a(n-5) -2124*a(n-6) +3302*a(n-7) +2396*a(n-8) +7504*a(n-9) +580*a(n-10) +1632*a(n-11) %e A224009 Some solutions for n=3 %e A224009 ..0..0..0..0..1....0..0..1..2..2....0..0..2..2..2....1..1..2..2..2 %e A224009 ..1..1..1..2..2....0..1..2..2..2....0..1..1..1..2....1..1..1..1..2 %e A224009 ..0..2..2..2..2....1..1..2..2..2....0..0..1..2..2....0..0..0..0..1 %K A224009 nonn %O A224009 1,1 %A A224009 _R. H. Hardin_ Mar 30 2013