A219422 Unchanging value maps: number of 2 X n binary arrays indicating the locations of corresponding elements unequal to no horizontal or antidiagonal neighbor in a random 0..2 2 X n array.

1, 7, 20, 57, 160, 454, 1292, 3676, 10452, 29724, 84548, 240480, 683968, 1945348, 5533040, 15737260, 44760324, 127308564, 362094824, 1029880752, 2929216636, 8331363064, 23696305892, 67397723860, 191694568548, 545223274608

Offset: 1

Author

R. H. Hardin, Nov 19 2012

Keywords

• nonn

Comments

Row 2 of A219421.

Examples

			Some solutions for n=3:
..0..0..0....1..0..1....0..0..1....0..0..0....1..0..0....0..0..1....0..0..0
..1..0..1....0..0..0....0..0..1....0..0..1....0..0..1....0..0..0....1..0..0
		

Links

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

Crossrefs

Cf. A219421.

Formula

Empirical: a(n) = 2*a(n-1) + a(n-2) + 3*a(n-3) + 4*a(n-4) - 2*a(n-5) - 4*a(n-6) for n>8.

Empirical g.f.: x*(1 + 5*x + 5*x^2 + 7*x^3 + x^4 - 9*x^5 - 9*x^6 - 2*x^7) / ((1 + 2*x^2)*(1 - 2*x - 3*x^2 + x^3 + 2*x^4)). - Colin Barker, Jul 26 2018