A206271 Number of (n+1) X 3 0..2 arrays with no 2 X 2 subblock having the number of clockwise edge increases equal to the number of counterclockwise edge increases in its adjacent leftward or upward neighbors.

306, 972, 3168, 11205, 35922, 123357, 408198, 1376754, 4572942, 15438600, 51367338, 172747923, 576448980, 1935886518, 6465571452, 21695411226, 72514916274, 243164479179, 813186470136, 2725748659476, 9118451550024

Offset

1,1

Comments

Column 2 of A206277.

Links

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

Formula

Empirical: a(n) = 8*a(n-2) +28*a(n-4) +36*a(n-5) -18*a(n-6) +78*a(n-7) -490*a(n-8) +298*a(n-9) +86*a(n-10) -854*a(n-11) +1669*a(n-12) -524*a(n-13) -872*a(n-14) +648*a(n-15) +140*a(n-16) -302*a(n-17) +10*a(n-18) +76*a(n-19) +8*a(n-20) -16*a(n-21) +8*a(n-22) for n>24.

Example

Some solutions for n=4:
..2..0..2....1..2..0....0..1..1....0..2..2....2..1..0....0..0..0....1..2..1
..1..1..0....1..0..1....2..1..1....0..1..2....2..2..1....1..2..0....0..1..1
..1..1..0....2..1..1....0..2..2....0..0..1....2..2..2....1..2..1....0..0..2
..1..2..1....2..1..1....0..2..2....0..0..1....0..2..2....0..0..2....2..1..0
..0..1..1....0..2..1....1..0..2....2..1..2....2..0..2....0..0..1....1..0..0

Crossrefs

Sequence in context: A005951 A294596 A294710 * A236012 A158589 A030030

Adjacent sequences: A206268 A206269 A206270 * A206272 A206273 A206274

Keyword

nonn

Author

R. H. Hardin, Feb 05 2012

Status

approved