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 A224021 #6 Jul 23 2025 04:52:49 %S A224021 56,3136,122523,4002738,120352359,3491241557,99853876444, %T A224021 2841637297963,80738139650660,2292943314015674,65111906248932329, %U A224021 1848921234461230235,52501963543862778240,1490846712885812140128,42334133889896297673617 %N A224021 Number of nX5 0..3 arrays with rows nondecreasing and antidiagonals unimodal. %C A224021 Column 5 of A224024 %H A224021 R. H. Hardin, <a href="/A224021/b224021.txt">Table of n, a(n) for n = 1..210</a> %F A224021 Empirical: a(n) = 56*a(n-1) -1098*a(n-2) +10776*a(n-3) -59038*a(n-4) +197135*a(n-5) -527776*a(n-6) +1780117*a(n-7) -5020078*a(n-8) +3603978*a(n-9) -19091082*a(n-10) +61460622*a(n-11) +49090018*a(n-12) +274177128*a(n-13) +105163104*a(n-14) +354022404*a(n-15) +28705280*a(n-16) +147891456*a(n-17) -1275168*a(n-18) +15980544*a(n-19) %e A224021 Some solutions for n=3 %e A224021 ..0..2..3..3..3....1..2..2..2..2....2..2..3..3..3....1..2..2..2..3 %e A224021 ..0..2..2..3..3....0..0..1..1..2....0..0..0..0..3....0..0..1..2..2 %e A224021 ..0..0..1..2..2....0..0..1..3..3....0..0..0..0..2....0..0..1..1..2 %K A224021 nonn %O A224021 1,1 %A A224021 _R. H. Hardin_ Mar 30 2013