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 A223988 #6 Jul 23 2025 04:46:26 %S A223988 20,400,5029,44803,308470,1738756,8350154,35158856,132595894, %T A223988 455284536,1441678804,4253578398,11791889562,30929283640,77204065141, %U A223988 184304047745,422556706314,933834642586,1995549087157,4134881948947,8327774224280 %N A223988 Number of 3Xn 0..3 arrays with rows unimodal and columns nondecreasing. %C A223988 Row 3 of A223987 %H A223988 R. H. Hardin, <a href="/A223988/b223988.txt">Table of n, a(n) for n = 1..210</a> %F A223988 Empirical: a(n) = (1/3629463552000)*n^18 + (1/44808192000)*n^17 + (10403/10461394944000)*n^16 + (10537/373621248000)*n^15 + (2915977/5230697472000)*n^14 + (6071381/747242496000)*n^13 + (748919/8211456000)*n^12 + (23111713/28740096000)*n^11 + (409218107/73156608000)*n^10 + (320706361/10450944000)*n^9 + (107018740483/804722688000)*n^8 + (467745209/1026432000)*n^7 + (10942630223/8895744000)*n^6 + (239853259979/93405312000)*n^5 + (882554800469/217945728000)*n^4 + (6093492161/1297296000)*n^3 + (4200944633/1029188160)*n^2 + (1784593/1021020)*n + 1 %e A223988 Some solutions for n=3 %e A223988 ..0..2..2....0..0..3....0..1..1....1..2..0....2..1..1....0..1..0....0..1..1 %e A223988 ..0..2..2....0..0..3....1..1..3....1..2..1....2..2..1....1..2..0....1..2..1 %e A223988 ..3..2..2....2..3..3....3..3..3....1..2..1....3..3..2....3..2..2....1..3..2 %K A223988 nonn %O A223988 1,1 %A A223988 _R. H. Hardin_ Mar 30 2013