A221405 Number of nX4 arrays of occupancy after each element stays put or moves to some horizontal or vertical neighbor, with every occupancy equal to zero or two.

4, 44, 436, 4518, 47156, 492102, 5133044, 53529806, 558164472, 5819704716, 60677191216, 632619159318, 6595610902832, 68764677891112, 716926331557236, 7474513869766556, 77927543824707370, 812454058048811426

Offset: 1

Author

R. H. Hardin Jan 15 2013

Keywords

• nonn

Comments

Column 4 of A221408

Examples

			Some solutions for n=3
..0..2..2..0....0..2..0..2....2..2..0..2....2..2..0..2....0..2..0..0
..2..2..0..0....0..2..0..2....0..0..0..2....0..2..0..0....2..0..0..2
..0..0..2..2....2..0..0..2....2..2..0..0....2..0..2..0....2..2..2..0
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..94

Formula

Empirical: a(n) = 19*a(n-1) -110*a(n-2) +250*a(n-3) -446*a(n-4) +939*a(n-5) -1112*a(n-6) -343*a(n-7) -822*a(n-8) +692*a(n-9) +1957*a(n-10) +2810*a(n-11) -1975*a(n-12) -59*a(n-13) -2679*a(n-14) +738*a(n-15) +1088*a(n-16) +1258*a(n-17) -418*a(n-18) -562*a(n-19) +192*a(n-20) +336*a(n-21) +32*a(n-22) -32*a(n-23)