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 A224000 #8 Aug 25 2018 16:15:40 %S A224000 9,31,76,155,281,469,736,1101,1585,2211,3004,3991,5201,6665,8416, %T A224000 10489,12921,15751,19020,22771,27049,31901,37376,43525,50401,58059, %U A224000 66556,75951,86305,97681,110144,123761,138601,154735,172236,191179,211641,233701 %N A224000 Number of 2 X n 0..2 arrays with antidiagonals unimodal and rows and diagonals nondecreasing. %C A224000 Row 2 of A223999. %H A224000 R. H. Hardin, <a href="/A224000/b224000.txt">Table of n, a(n) for n = 1..210</a> %F A224000 Empirical: a(n) = (1/12)*n^4 + 1*n^3 + (41/12)*n^2 + (7/2)*n + 1. %F A224000 Conjectures from _Colin Barker_, Aug 25 2018: (Start) %F A224000 G.f.: x*(9 - 14*x + 11*x^2 - 5*x^3 + x^4) / (1 - x)^5. %F A224000 a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>5. %F A224000 (End) %e A224000 Some solutions for n=3: %e A224000 ..0..0..2....0..0..1....1..1..1....0..1..1....1..1..1....0..0..2....1..1..2 %e A224000 ..0..0..2....2..2..2....0..1..2....0..1..2....0..1..1....2..2..2....0..2..2 %Y A224000 Cf. A223999. %K A224000 nonn %O A224000 1,1 %A A224000 _R. H. Hardin_, Mar 30 2013