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 A223791 #6 Jul 23 2025 04:31:07 %S A223791 81,6561,151580,1560013,11012718,61333566,288823579,1196519547, %T A223791 4468789562,15293854291,48524120300,143996244303,402491787780, %U A223791 1065874328092,2687501352957,6479586585575,14994608609716,33416226803133 %N A223791 Number of 4Xn 0..2 arrays with rows, diagonals and antidiagonals unimodal. %C A223791 Row 4 of A223789 %H A223791 R. H. Hardin, <a href="/A223791/b223791.txt">Table of n, a(n) for n = 1..210</a> %F A223791 Empirical: a(n) = (456419/5230697472000)*n^16 + (165527/653837184000)*n^15 + (1160527/37362124800)*n^14 + (4098907/18681062400)*n^13 - (2323961/28740096000)*n^12 + (686821469/7185024000)*n^11 - (1282316951/1828915200)*n^10 + (6465409549/914457600)*n^9 + (69811138547/5225472000)*n^8 - (199799815457/326592000)*n^7 + (10755338490607/1437004800)*n^6 - (18136370082679/359251200)*n^5 + (23466839810116957/108972864000)*n^4 - (2416825957955693/4540536000)*n^3 + (2240986165151/4324320)*n^2 + (7139372965/18018)*n - 659081 for n>8 %e A223791 Some solutions for n=3 %e A223791 ..1..1..1....0..1..0....1..1..0....0..1..2....0..2..0....0..0..1....1..2..0 %e A223791 ..0..2..0....0..2..0....2..2..2....2..1..0....0..1..1....1..0..0....0..1..1 %e A223791 ..2..1..0....0..0..2....0..2..2....1..1..0....0..1..2....0..1..0....1..2..0 %e A223791 ..1..1..0....0..1..0....1..2..1....1..2..1....2..2..1....0..2..1....1..1..2 %K A223791 nonn %O A223791 1,1 %A A223791 _R. H. Hardin_ Mar 27 2013