A213698 Half the number of 3 X 3 0..n symmetric arrays with no 2 X 2 subblock summing to 2n.

13, 192, 1320, 5470, 17499, 45892, 105856, 219564, 421825, 758560, 1296408, 2117882, 3336655, 5087460, 7549184, 10927192, 15486741, 21525024, 29417800, 39578070, 52519203, 68796772, 89091840, 114132100, 144799369, 182025792

Offset

1,1

Comments

Row 2 of A213697.

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + a(n-2) - 11*a(n-3) + 6*a(n-4) + 14*a(n-5) - 14*a(n-6) - 6*a(n-7) + 11*a(n-8) - a(n-9) - 3*a(n-10) + a(n-11).

Empirical g.f.: x*(13 + 153*x + 731*x^2 + 1461*x^3 + 1803*x^4 + 1111*x^5 + 425*x^6 + 59*x^7 + 4*x^8) / ((1 - x)^7*(1 + x)^4). - Colin Barker, Jul 22 2018

Example

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

Crossrefs

Cf. A213697.

Sequence in context: A103731 A331495 A000563 * A159196 A177508 A228659

Adjacent sequences: A213695 A213696 A213697 * A213699 A213700 A213701

Keyword

nonn

Author

R. H. Hardin, Jun 18 2012

Status

approved