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 A224020 #6 Jul 23 2025 04:52:32 %S A224020 35,1225,32523,772683,17735200,403836633,9186127249,208983591829, %T A224020 4754911670136,108190494364824,2461721043138176,56012981686098087, %U A224020 1274495739407259502,28999333370466443973,659838457829407289280 %N A224020 Number of nX4 0..3 arrays with rows nondecreasing and antidiagonals unimodal. %C A224020 Column 4 of A224024 %H A224020 R. H. Hardin, <a href="/A224020/b224020.txt">Table of n, a(n) for n = 1..210</a> %F A224020 Empirical: a(n) = 35*a(n-1) -347*a(n-2) +1689*a(n-3) -2986*a(n-4) -2311*a(n-5) +23532*a(n-6) -23864*a(n-7) -36468*a(n-8) +100464*a(n-9) +94080*a(n-10) %e A224020 Some solutions for n=3 %e A224020 ..2..2..3..3....0..1..1..1....0..0..0..1....0..1..2..3....0..1..1..1 %e A224020 ..2..2..3..3....0..2..2..3....0..0..1..2....0..0..3..3....1..3..3..3 %e A224020 ..1..1..2..3....0..0..0..0....0..0..1..1....0..2..3..3....2..3..3..3 %K A224020 nonn %O A224020 1,1 %A A224020 _R. H. Hardin_ Mar 30 2013