A188976 Number of nX2 array permutations with each element moved but moved no more than a city block distance of two.

1, 9, 116, 900, 7836, 71865, 640513, 5706113, 51056136, 456396688, 4078122040, 36448590305, 325763780945, 2911451082361, 26020738951500, 232557947597540, 2078461123504804, 18576017680577225, 166021162669244641

Offset: 1

Author

R. H. Hardin Apr 14 2011

Keywords

• nonn

Comments

Column 2 of A188981

Examples

			Some solutions for 3X2
..1..5....1..0....2..5....2..3....2..0....3..5....1..0....2..3....4..0....4..0
..4..2....3..5....1..0....5..4....5..1....1..2....5..4....0..1....1..2....1..5
..0..3....2..4....3..4....0..1....3..4....0..4....3..2....5..4....5..3....3..2
		

Links

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

Formula

Empirical: a(n) = 8*a(n-1) +3*a(n-2) +68*a(n-3) -142*a(n-4) -354*a(n-5) +225*a(n-6) +430*a(n-7) +47*a(n-8) +308*a(n-9) -16*a(n-10) -932*a(n-11) +281*a(n-12) +24*a(n-13) -195*a(n-14) +112*a(n-15) +22*a(n-16) +22*a(n-17) -a(n-18) -6*a(n-19) +a(n-20)