A269196 - OEIS

%I #8 Jan 20 2019 06:25:58

%S 60,1284,25572,471492,8314020,142233732,2380537188,39186271044,

%T 636703584804,10237337586180,163189207436004,2582623154662596,

%U 40622651914004388,635603382950474628,9899530341266770020

%N Number of n X 3 0..3 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling three no more than once.

%H R. H. Hardin, <a href="/A269196/b269196.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 30*a(n-1) -237*a(n-2) +180*a(n-3) -36*a(n-4) for n>5.

%F Empirical g.f.: 12*x*(1 - 6*x)*(5 - 13*x + 28*x^2 - 12*x^3) / (1 - 15*x + 6*x^2)^2. - _Colin Barker_, Jan 20 2019

%e Some solutions for n=3:

%e ..3..1..1. .2..3..2. .3..1..0. .1..0..1. .2..0..3. .3..3..3. .3..3..3

%e ..3..1..0. .2..2..0. .0..0..1. .1..3..2. .2..3..2. .3..1..1. .3..3..2

%e ..0..2..3. .2..2..2. .0..1..0. .0..0..2. .3..2..2. .1..0..1. .3..2..3

%Y Column 3 of A269201.

%K nonn

%O 1,1

%A _R. H. Hardin_, Feb 20 2016