A250678 Number of (2+1)X(n+1) 0..3 arrays with nondecreasing x(i,j)+x(i,j-1) in the i direction and nondecreasing absolute value of x(i,j)-x(i-1,j) in the j direction.

520, 5154, 42422, 329226, 2406972, 16949262, 115965426, 777137322, 5127532140, 33440743748, 216192271674, 1388450185042, 8872367832376, 56479411574776, 358489567889570, 2270374738759036, 14354245060678584, 90635411405776404

Offset: 1

Author

R. H. Hardin, Nov 26 2014

Keywords

• nonn

Comments

Row 2 of A250676

Examples

			Some solutions for n=3
..2..2..1..0....3..1..0..0....3..1..1..1....3..0..3..1....0..1..0..1
..3..1..2..2....3..2..1..1....2..2..2..2....2..2..1..3....1..2..1..2
..2..2..3..1....2..3..2..2....2..2..3..3....1..3..3..1....1..2..2..3
		

Links

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

Formula

Empirical: a(n) = 19*a(n-1) -115*a(n-2) +64*a(n-3) +1793*a(n-4) -4621*a(n-5) -9264*a(n-6) +41507*a(n-7) +14863*a(n-8) -173352*a(n-9) +31915*a(n-10) +399081*a(n-11) -166415*a(n-12) -530154*a(n-13) +278712*a(n-14) +400256*a(n-15) -230016*a(n-16) -156992*a(n-17) +92352*a(n-18) +24192*a(n-19) -13824*a(n-20)