A223660 Number of nX2 0..3 arrays with row sums unimodal and column sums inverted unimodal.

16, 256, 3060, 29922, 252912, 1912914, 13254601, 85563043, 521069404, 3022541224, 16826714534, 90449485556, 471770734372, 2397374836954, 11909366979539, 57999389713133, 277578926336176, 1308191004875392, 6081976574677816, 27936365857925926, 126946765412455656

Offset: 1

Author

R. H. Hardin, Mar 25 2013

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 2 of A223663.

Formula

Empirical: a(n) = 31*a(n-1) -437*a(n-2) +3707*a(n-3) -21099*a(n-4) +85029*a(n-5) -249431*a(n-6) +538841*a(n-7) -856504*a(n-8) +988504*a(n-9) -804432*a(n-10) +436752*a(n-11) -141696*a(n-12) +20736*a(n-13).

Empirical g.f.: -x*( 16 -240*x +2116*x^2 -12378*x^3 +51142*x^4 -153984*x^5 +342369*x^6 -562536*x^7 +675688*x^8 -578496*x^9 +336528*x^10 -120960*x^11 +20736*x^12) / ( (-1+4*x)^2 *(x-1)^3 *(3*x-1)^4 *(2*x-1)^4 ). - R. J. Mathar, May 17 2014