A185515 Number of (n+1) X 4 0..2 arrays with every 2 X 2 subblock singular.

593, 12361, 154561, 2490449, 35659489, 541370505, 7998109489, 119752453041, 1781802607473, 26592505725449, 396308610878561, 5910310463665361, 88113720913502145, 1313850510428863561, 19589143573382779985

Offset: 1

Author

R. H. Hardin, Jan 29 2011

Keywords

• nonn

Comments

Column 3 of A185521.

Examples

			Some solutions for 3 X 4:
..1..1..1..2....1..2..1..2....1..2..2..2....2..0..2..1....2..0..0..1
..0..0..0..0....0..0..0..0....0..0..0..0....2..0..0..0....2..0..0..1
..0..1..0..0....1..2..0..2....1..0..1..0....2..0..2..2....2..0..0..2
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A185521.

Formula

Empirical: a(n) = 21*a(n-1) - 47*a(n-2) - 1009*a(n-3) + 5624*a(n-4) - 3060*a(n-5) - 27360*a(n-6) + 36864*a(n-7).

Empirical g.f.: x*(593 - 92*x - 77149*x^2 + 423972*x^3 - 238356*x^4 - 2179296*x^5 + 2985984*x^6) / (1 - 21*x + 47*x^2 + 1009*x^3 - 5624*x^4 + 3060*x^5 + 27360*x^6 - 36864*x^7). - Colin Barker, Apr 16 2018