A203365 - OEIS

%I #8 Jun 04 2018 05:47:26

%S 2,9,30,110,390,1399,4998,17881,63940,228680,817820,2924801,10460002,

%T 37408329,133784090,478454630,1711106370,6119462399,21885149998,

%U 78268279361,279912339880,1001055838960,3580095086040,12803562326001

%N Number of n X 2 0..2 arrays with every 1 immediately preceded by 0 to the left or above, and every 2 immediately preceded by both a 1 and a 0.

%C Column 2 of A203371.

%H R. H. Hardin, <a href="/A203365/b203365.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 2*a(n-1) +5*a(n-2) +2*a(n-3) +a(n-4).

%F Empirical g.f.: x*(2 + 5*x + 2*x^2 + x^3) / (1 - 2*x - 5*x^2 - 2*x^3 - x^4). - _Colin Barker_, Jun 04 2018

%e Some solutions for n=4:

%e ..0..1....0..0....0..0....0..0....0..1....0..0....0..1....0..1....0..0....0..0

%e ..1..0....0..0....0..0....0..0....0..2....0..0....0..1....0..1....0..0....1..1

%e ..0..0....1..0....1..2....0..0....1..0....0..0....0..0....0..2....0..1....0..0

%e ..1..2....0..0....0..0....0..1....0..1....0..0....0..1....0..0....0..0....0..1

%Y Cf. A203371.

%K nonn

%O 1,1

%A _R. H. Hardin_, Dec 31 2011