A213699 Half the number of 4X4 0..n symmetric arrays with no 2X2 subblock summing to 2n.

70, 7827, 208072, 2322599, 16537086, 84059234, 342943680, 1169405354, 3500184570, 9372540629, 23022951048, 52423261153, 112270651514, 227577256564, 440658095360, 818409534692, 1466948929086, 2544850623111, 4291394833480

Offset: 1

Author

R. H. Hardin Jun 18 2012

Keywords

• nonn

Comments

Row 3 of A213697

Examples

			Some solutions for n=4
..0..3..4..0....2..3..1..3....3..0..4..4....2..3..2..2....0..1..2..2
..3..3..2..3....3..4..3..3....0..2..4..3....3..2..0..0....1..4..2..4
..4..2..2..2....1..3..1..0....4..4..0..4....2..0..3..1....2..2..1..0
..0..3..2..3....3..3..0..3....4..3..4..3....2..0..1..0....2..4..0..2
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..144

Formula

Empirical: a(n) = 3*a(n-1) +5*a(n-2) -23*a(n-3) -4*a(n-4) +76*a(n-5) -28*a(n-6) -140*a(n-7) +98*a(n-8) +154*a(n-9) -154*a(n-10) -98*a(n-11) +140*a(n-12) +28*a(n-13) -76*a(n-14) +4*a(n-15) +23*a(n-16) -5*a(n-17) -3*a(n-18) +a(n-19)