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 A224312 #6 Jul 23 2025 05:05:56 %S A224312 81,1944,11361,45453,164514,562760,1825800,5585818,16074063,43567313, %T A224312 111632420,271667665,630966702,1405080075,3012670262,6242914246, %U A224312 12544093805,24510622826,46689053477,86888070112,158272032306 %N A224312 Number of 4Xn 0..2 arrays with diagonals and rows unimodal and antidiagonals nondecreasing. %C A224312 Row 4 of A224310 %H A224312 R. H. Hardin, <a href="/A224312/b224312.txt">Table of n, a(n) for n = 1..210</a> %F A224312 Empirical: a(n) = (1/106748928000)*n^16 + (1/13343616000)*n^15 + (89/9340531200)*n^14 + (5179/37362124800)*n^13 + (126779/28740096000)*n^12 + (103081/1306368000)*n^11 + (18019/13063680)*n^10 - (76841/261273600)*n^9 + (81547771/746496000)*n^8 + (262193969/1306368000)*n^7 - (318727393/1437004800)*n^6 + (10868710291/359251200)*n^5 - (1656836125459/15567552000)*n^4 + (975909282919/1297296000)*n^3 - (26075217263/10810800)*n^2 + (77958821/8190)*n - 17954 for n>6 %e A224312 Some solutions for n=3 %e A224312 ..0..1..0....1..0..0....2..2..2....0..1..0....0..1..0....2..1..1....1..1..1 %e A224312 ..1..2..1....1..2..1....2..2..0....2..0..0....1..2..1....1..1..2....1..1..0 %e A224312 ..2..2..2....2..1..1....2..1..0....0..0..0....2..1..0....1..2..0....2..1..1 %e A224312 ..2..2..1....2..2..1....1..1..1....2..0..0....1..1..2....2..0..0....1..2..1 %K A224312 nonn %O A224312 1,1 %A A224312 _R. H. Hardin_ Apr 03 2013