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 A189274 #21 Jul 22 2025 11:39:44
%S A189274 1,9,45,225,1125,5625,28125,140625,703125,3515625,17578125,87890625,
%T A189274 439453125,2197265625,10986328125,54931640625,274658203125,
%U A189274 1373291015625,6866455078125,34332275390625,171661376953125,858306884765625,4291534423828125,21457672119140625
%N A189274 Number of nX3 array permutations with each element not moved or moved diagonally or antidiagonally by one.
%C A189274 Column 3 of A189280
%H A189274 R. H. Hardin, <a href="/A189274/b189274.txt">Table of n, a(n) for n = 1..200</a>
%H A189274 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (5).
%F A189274 Empirical: a(n) = 5*a(n-1) for n>2
%F A189274 Apparently, the O.g.f. is x*(1+4x)/(1-5x). - _Philippe Deléham_, Feb 25 2012
%F A189274 Apparently : a(n) = Sum_{k, 1<=k<=n} A207628(n,k)*2^(k-1). - _Philippe Deléham_, Feb 25 2012
%e A189274 Some solutions for 4X3
%e A189274 ..0..1..4....0..1..4....4..5..2....4..1..2....0..5..2....0..5..2....0..5..2
%e A189274 ..3..2..5....3..2..5....3..0..1....3..0..5....3..8..1....7..4..1....3..4..1
%e A189274 .10.11..8....6..7..8...10.11..8....6..9.10....6.11..4...10..3..8....6..7..8
%e A189274 ..9..6..7....9.10.11....9..6..7....7..8.11....9.10..7....9..6.11....9.10.11
%Y A189274 Cf. A270567.
%K A189274 nonn
%O A189274 1,2
%A A189274 _R. H. Hardin_ Apr 19 2011