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 A223828 #6 Jul 23 2025 04:34:38 %S A223828 86,7396,310396,7291180,111026387,1215505987,10278415020,70637615542, %T A223828 409495177832,2059270878998,9178828735664,36883354080922, %U A223828 135437433227956,459525932946746,1453793476211931,4321377067061981,12146690423924810 %N A223828 Number of nX5 0..2 arrays with rows and columns unimodal. %C A223828 Column 5 of A223831 %H A223828 R. H. Hardin, <a href="/A223828/b223828.txt">Table of n, a(n) for n = 1..210</a> %F A223828 Empirical: a(n) = (63370093/405483668029440000)*n^20 + (71859847/9357315416064000)*n^19 + (33442223/166295420928000)*n^18 + (7404500641/2134124568576000)*n^17 + (27079914203/627683696640000)*n^16 + (25382116619/62768369664000)*n^15 + (28390454557/9656672256000)*n^14 + (289526123249/17118646272000)*n^13 + (3238876266163/41385738240000)*n^12 + (2848501575259/9656672256000)*n^11 + (17668229482801/19313344512000)*n^10 + (22667715892433/9656672256000)*n^9 + (5949755731841/1188794880000)*n^8 + (32017686101257/3621252096000)*n^7 + (12478274965523/960740352000)*n^6 + (13604598171413/871782912000)*n^5 + (866466410064373/55576160640000)*n^4 + (13639237471/1122750720)*n^3 + (178704902203/22562971200)*n^2 + (15738662/4849845)*n + 1 %e A223828 Some solutions for n=3 %e A223828 ..0..1..2..2..0....0..0..0..0..0....0..0..0..1..1....0..1..0..0..0 %e A223828 ..0..0..0..2..0....0..0..1..0..0....0..1..2..1..1....0..2..2..2..0 %e A223828 ..0..0..0..2..2....1..1..1..1..0....1..2..2..0..0....0..1..1..2..1 %K A223828 nonn %O A223828 1,1 %A A223828 _R. H. Hardin_ Mar 27 2013