A184096 Half the number of n X n toroidal binary arrays with each element having the sum of its vertical neighbors equal to the sum of its horizontal neighbors

1, 2, 7, 18, 31, 98, 127, 450, 511, 1922, 2047, 7938, 8191, 32258, 32767, 130050, 131071, 522242, 524287, 2093058

Offset

1,2

Comments

Half the number of solutions in 0..1 of a 1-d velocity-one wave equation utt=uxx on a periodic grid

Diagonal of A184097

Links

Table of n, a(n) for n=1..20.

Formula

Empirical G.f.: x*(1+2*x-2*x^2)*(1+2*x^2)/(1-x)/(1+x)/(1-2*x)/(1+2*x)/(1-2*x^2). [Colin Barker, Feb 17 2012]

Example

Some solutions for 5X5
..1..0..0..1..1....1..0..0..0..1....1..0..0..0..0....1..1..1..0..0
..0..0..1..1..1....1..1..0..0..0....0..1..0..0..0....0..1..1..1..0
..0..1..1..1..0....0..1..1..0..0....0..0..1..0..0....0..0..1..1..1
..1..1..1..0..0....0..0..1..1..0....0..0..0..1..0....1..0..0..1..1
..1..1..0..0..1....0..0..0..1..1....0..0..0..0..1....1..1..0..0..1

Crossrefs

Sequence in context: A001114 A107615 A195605 * A136583 A307684 A141631

Adjacent sequences: A184093 A184094 A184095 * A184097 A184098 A184099

Keyword

nonn

Author

R. H. Hardin Jan 09 2011

Status

approved