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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A221652 Number of n X 2 arrays of occupancy after each element moves to some horizontal, diagonal or antidiagonal neighbor, without move-in move-out left turns. 2
 1, 4, 12, 40, 136, 460, 1556, 5264, 17808, 60244, 203804, 689464, 2332440, 7890588, 26693668, 90304032, 305496352, 1033486756, 3496260652, 11827765064, 40013042600, 135363153516, 457930268212, 1549167000752, 5240794423984 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Column 2 of A221655. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 3*a(n-1) + a(n-2) + a(n-3) for n>4. Empirical g.f.: x*(1 - x)*(1 + x)^2 / (1 - 3*x - x^2 - x^3). - Colin Barker, Mar 14 2018 EXAMPLE Some solutions for n=3: ..0..2....0..1....1..1....2..1....1..1....0..1....0..1....1..1....0..2....1..1 ..2..1....2..1....1..1....0..0....0..2....2..2....1..2....1..2....2..0....0..1 ..1..0....1..1....1..1....1..2....2..0....1..0....2..0....1..0....1..1....2..1 CROSSREFS Cf. A221655. Sequence in context: A289653 A081875 A102433 * A259806 A100320 A064649 Adjacent sequences: A221649 A221650 A221651 * A221653 A221654 A221655 KEYWORD nonn AUTHOR R. H. Hardin, Jan 21 2013 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.

Last modified September 27 20:41 EDT 2023. Contains 365714 sequences. (Running on oeis4.)