A220407 Equals two maps: number of 2 X n binary arrays indicating the locations of corresponding elements equal to exactly two of their horizontal, diagonal and antidiagonal neighbors in a random 0..1 2 X n array.

1, 6, 17, 40, 93, 206, 431, 924, 1863, 3898, 7773, 15992, 31825, 64758, 128963, 260596, 519603, 1045490, 2086817, 4188144, 8365965, 16764910, 33505143, 67084268, 134111071, 268386282, 536641349, 1073643496, 2146991913, 4294770662

Offset

1,2

Comments

Row 2 of A220406.

Links

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

Formula

Empirical: a(n) = 2*a(n-1) + 7*a(n-2) - 14*a(n-3) - 19*a(n-4) + 38*a(n-5) + 25*a(n-6) - 50*a(n-7) - 16*a(n-8) + 32*a(n-9) + 4*a(n-10) - 8*a(n-11).

Empirical g.f.: x*(1 + 4*x - 2*x^2 - 22*x^3 - 3*x^4 + 54*x^5 - 2*x^6 - 64*x^7 + 20*x^8 + 32*x^9 - 16*x^10) / ((1 - x)^3*(1 + x)^3*(1 - 2*x)*(1 - 2*x^2)^2). - Colin Barker, Jul 31 2018

Example

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

Crossrefs

Cf. A220406.

Sequence in context: A061349 A213780 A101945 * A013319 A047861 A370589

Adjacent sequences: A220404 A220405 A220406 * A220408 A220409 A220410

Keyword

nonn

Author

R. H. Hardin, Dec 13 2012

Status

approved