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 A224027 #6 Jul 23 2025 04:54:11 %S A224027 1024,100000,1859020,17735200,120352359,646270418,2903448338, %T A224027 11324147154,39352493380,124192808325,361131166470,978546580876, %U A224027 2493201619797,6016880535375,13837190690133,30477772502130,64570854690796 %N A224027 Number of 5Xn 0..3 arrays with rows nondecreasing and antidiagonals unimodal. %C A224027 Row 5 of A224024 %H A224027 R. H. Hardin, <a href="/A224027/b224027.txt">Table of n, a(n) for n = 1..210</a> %F A224027 Empirical: a(n) = (769/444787200)*n^15 + (781507/10897286400)*n^14 + (732989/444787200)*n^13 + (6062213/239500800)*n^12 + (4527293/15966720)*n^11 + (49818529/21772800)*n^10 + (300432343/21772800)*n^9 + (9176781683/152409600)*n^8 + (2072451091/10886400)*n^7 + (1971136933/4354560)*n^6 + (16020797923/19958400)*n^5 + (55454431657/59875200)*n^4 - (688455589/2402400)*n^3 - (18610604083/37837800)*n^2 + (69728249/15015)*n + 2530 for n>3 %e A224027 Some solutions for n=3 %e A224027 ..0..0..2....0..0..2....0..0..2....0..0..2....0..0..0....0..0..0....0..0..0 %e A224027 ..0..2..3....0..2..2....0..2..3....0..0..2....0..0..1....0..2..2....0..0..2 %e A224027 ..1..3..3....0..2..3....1..2..3....0..2..3....1..1..1....0..0..0....0..2..3 %e A224027 ..0..1..3....2..3..3....0..1..2....2..3..3....1..2..2....0..0..1....1..2..2 %e A224027 ..0..3..3....1..1..3....0..0..0....2..2..3....1..1..2....0..0..3....1..3..3 %K A224027 nonn %O A224027 1,1 %A A224027 _R. H. Hardin_ Mar 30 2013