A280674 Number of 2 X n 0..2 arrays with no element equal to more than one of its horizontal and antidiagonal neighbors and with new values introduced in order 0 sequentially upwards.

2, 11, 59, 338, 1917, 10893, 61880, 351541, 1997095, 11345458, 64453321, 366158041, 2080136592, 11817214849, 67133363931, 381383313234, 2166631062437, 12308588230773, 69924846394792, 397241669934877, 2256722073320511

Offset: 1

Author

R. H. Hardin, Jan 07 2017

Keywords

• nonn

Examples

			Some solutions for n=4:
..0..0..1..0. .0..1..0..2. .0..1..1..2. .0..1..0..1. .0..0..1..2
..2..0..2..1. .1..2..0..2. .0..2..0..2. .1..0..2..2. .1..0..0..1
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Crossrefs

Row 2 of A280673.

Formula

Empirical: a(n) = 5*a(n-1) + 6*a(n-2) - 11*a(n-3) - 7*a(n-4) + 4*a(n-5) for n>6.

Empirical g.f.: x*(1 - x)*(2 + 3*x - x^2)*(1 - 2*x^2) / ((1 + x)*(1 - 6*x + 11*x^3 - 4*x^4)). - Colin Barker, Feb 14 2019