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

1,1

Comments

Row 3 of A213697

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)

Example

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

Crossrefs

Sequence in context: A363296 A049216 A229477 * A184275 A179713 A330244

Adjacent sequences: A213696 A213697 A213698 * A213700 A213701 A213702

Keyword

nonn

Author

R. H. Hardin Jun 18 2012

Status

approved