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 A212940 #9 Jul 22 2025 23:00:23 %S A212940 1,1016501,10058484751,52311221188001,212180664326328751, %T A212940 764898125476357657001,2592491557886605293297751, %U A212940 8492622463881130571398876001,27285563319283684654297283766751 %N A212940 Number of nX5 0..4 arrays with no column j greater than or equal to than column j-1 in all rows. %C A212940 Column 5 of A212943 %H A212940 R. H. Hardin, <a href="/A212940/b212940.txt">Table of n, a(n) for n = 1..210</a> %F A212940 Empirical: a(n) = 8001*a(n-1) -24144750*a(n-2) +35582371250*a(n-3) -27539217890625*a(n-4) +11055908759765625*a(n-5) -2081011816406250000*a(n-6) +133539505004882812500*a(n-7). %F A212940 Empirical: a(n) = -2*350^n+3*875^n+3*1125^n+3125^n+126^n-4*1875^n-2*525^n. _R. J. Mathar_, Jun 27 2012 %e A212940 Some solutions for n=4 %e A212940 ..3..0..3..3..1....3..4..4..3..2....0..4..4..3..0....3..2..4..0..0 %e A212940 ..4..1..1..3..3....0..1..3..1..4....2..1..1..4..3....0..3..4..0..4 %e A212940 ..3..3..1..2..0....1..0..2..0..1....1..2..0..3..2....3..1..3..0..1 %e A212940 ..4..0..4..3..4....4..2..0..3..0....3..0..1..2..0....2..1..0..3..0 %K A212940 nonn %O A212940 1,2 %A A212940 _R. H. Hardin_ May 31 2012