A252870 - OEIS

%I #9 Nov 22 2015 13:19:33

%S 0,1,8,26,61,120,211,343,526,771,1090,1496,2003,2626,3381,4285,5356,

%T 6613,8076,9766,11705,13916,16423,19251,22426,25975,29926,34308,39151,

%U 44486,50345,56761,63768,71401,79696,88690,98421,108928,120251,132431,145510

%N Number of n X 2 nonnegative integer arrays with upper left 0 and lower right n+2-4 and value increasing by 0 or 1 with every step right or down.

%C Column 2 of A252876.

%H R. H. Hardin, <a href="/A252870/b252870.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = (1/24)*n^4 + (5/12)*n^3 - (13/24)*n^2 - (11/12)*n + 1.

%F Empirical: G.f.: -x^2*(1+3*x-4*x^2+x^3) / (x-1)^5. - _R. J. Mathar_, Nov 21 2015

%e All solutions for n=3:

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

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

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

%K nonn

%O 1,3

%A _R. H. Hardin_, Dec 24 2014