login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Row 2 of A220406.
LINKS
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 13 2012
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 29 04:23 EDT 2024. Contains 371264 sequences. (Running on oeis4.)