A204223 Number of (n+1)X2 0..2 arrays with the sums of 2X2 subblocks nondecreasing rightwards and downwards.

81, 450, 2500, 11100, 49284, 192474, 751689, 2707641, 9753129, 33291180, 113635600, 373782240, 1229484096, 3940246872, 12627691129, 39725765841, 124974269289, 387960161310, 1204352604900, 3702976839180, 11385401099076

Offset: 1

Author

R. H. Hardin Jan 13 2012

Keywords

• nonn

Comments

Column 1 of A204230

Examples

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

Links

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

Formula

Empirical: a(n) = 9*a(n-1) -2*a(n-2) -210*a(n-3) +498*a(n-4) +1782*a(n-5) -7500*a(n-6) -4716*a(n-7) +53007*a(n-8) -25623*a(n-9) -209346*a(n-10) +253710*a(n-11) +460144*a(n-12) -940824*a(n-13) -427120*a(n-14) +1906032*a(n-15) -338256*a(n-16) -2148336*a(n-17) +1287648*a(n-18) +1144800*a(n-19) -1233792*a(n-20) -62208*a(n-21) +414720*a(n-22) -124416*a(n-23)