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 A223757 #6 Jul 23 2025 04:28:24 %S A223757 50,2500,61733,916107,9478535,74824917,477860225,2571238699, %T A223757 12006271464,49749360288,186123469150,637408917764,2020521264556, %U A223757 5982701793264,16672986760595,44013068603319,110650947588800,266164581427718 %N A223757 Number of nX3 0..3 arrays with rows, antidiagonals and columns unimodal. %C A223757 Column 3 of A223762 %H A223757 R. H. Hardin, <a href="/A223757/b223757.txt">Table of n, a(n) for n = 1..210</a> %F A223757 Empirical: a(n) = (89/169374965760)*n^18 + (673039/29640619008000)*n^17 + (5753323/10461394944000)*n^16 + (20639/2335132800)*n^15 + (5460977/52306974720)*n^14 + (350675333/373621248000)*n^13 + (34569853/5225472000)*n^12 + (744079211/20118067200)*n^11 + (1214093389/7315660800)*n^10 + (3120210973/5225472000)*n^9 + (1381865894063/804722688000)*n^8 + (2224350329/574801920)*n^7 + (252375235967/37362124800)*n^6 + (1486577243227/163459296000)*n^5 + (2159143550149/217945728000)*n^4 + (154699301/14414400)*n^3 - (959722661/467812800)*n^2 + (50040773/6126120)*n + 1 %e A223757 Some solutions for n=3 %e A223757 ..1..1..3....1..2..2....0..0..2....1..3..1....0..1..3....3..2..1....0..3..2 %e A223757 ..2..2..2....1..3..3....0..3..2....2..1..1....3..3..2....0..3..3....1..3..2 %e A223757 ..2..2..0....1..3..3....0..1..3....0..1..3....3..1..0....0..2..2....1..2..1 %K A223757 nonn %O A223757 1,1 %A A223757 _R. H. Hardin_ Mar 27 2013