A220549 Number of ways to reciprocally link elements of an nX4 array either to themselves or to exactly one horizontal, vertical or antidiagonal neighbor.

5, 108, 1814, 32173, 565061, 9943416, 174911750, 3077034244, 54130248568, 952245176313, 16751640356635, 294690365449276, 5184113807856060, 91197538858856819, 1604322628219475789, 28222813114190945744

Offset: 1

Author

R. H. Hardin Dec 15 2012

Keywords

• nonn

Comments

Column 4 of A220553

Examples

			Some solutions for n=3 0=self 2=n 3=ne 4=w 6=e 7=sw 8=s (reciprocal directions total 10)
..6..4..7..8....0..0..6..4....6..4..7..7....8..8..0..7....6..4..7..7
..0..3..0..2....0..7..0..8....0..3..3..0....2..2..3..0....0..3..3..0
..6..4..6..4....3..0..0..2....6..4..0..0....0..0..0..0....6..4..6..4
		

Links

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

Formula

Empirical: a(n) = 11*a(n-1) +111*a(n-2) +127*a(n-3) -649*a(n-4) -981*a(n-5) +1615*a(n-6) +2067*a(n-7) -2349*a(n-8) -1177*a(n-9) +1383*a(n-10) +199*a(n-11) -337*a(n-12) +3*a(n-13) +31*a(n-14) -a(n-15) -a(n-16)