A208873 - OEIS

%I #9 Jul 07 2018 08:51:27

%S 2,12,136,1798,24472,334618,4578580,62655190,857412640,11733394642,

%T 160567489036,2197311225838,30069453572632,411490201499818,

%U 5631102858140740,77059719245016070,1054535937228511120

%N Number of 2 X n 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or right-upward antidiagonal neighbors.

%C Row 2 of A208872.

%H R. H. Hardin, <a href="/A208873/b208873.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 18*a(n-1) - 65*a(n-2) + 84*a(n-3) - 36*a(n-4) for n>5.

%F Empirical g.f.: 2*x*(1 - 12*x + 25*x^2 - 19*x^3 + 6*x^4) / ((1 - x)*(1 - 2*x)*(1 - 15*x + 18*x^2)). - _Colin Barker_, Jul 07 2018

%e Some solutions for n=4:

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

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

%Y Cf. A208872.

%K nonn

%O 1,1

%A _R. H. Hardin_, Mar 02 2012