A275038 Number of 3 X n 0..2 arrays with no element equal to any value at offset (0,-1) (-1,-2) or (-2,0) and new values introduced in order 0..2.

3, 18, 46, 137, 401, 1152, 3336, 9720, 28277, 82174, 238829, 694135, 2017380, 5863430, 17042197, 49533046, 143966504, 418434888, 1216170841, 3534771986, 10273734201, 29860375290, 86788495974, 252248762928, 733155217213

Offset

1,1

Links

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

Formula

Empirical: a(n) = 3*a(n-1) - 2*a(n-2) + 4*a(n-3) + a(n-4) + 3*a(n-5) + 8*a(n-6) + a(n-7) - 3*a(n-8) - a(n-9) for n>10.

Empirical g.f.: x*(3 + 9*x - 2*x^2 + 23*x^3 + 7*x^4 + 12*x^5 + 10*x^6 - 10*x^7 - 8*x^8 - x^9) / (1 - 3*x + 2*x^2 - 4*x^3 - x^4 - 3*x^5 - 8*x^6 - x^7 + 3*x^8 + x^9). - Colin Barker, Jan 31 2019

Example

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

Crossrefs

Row 3 of A275037.

Sequence in context: A365442 A094159 A138976 * A304976 A364599 A064043

Adjacent sequences: A275035 A275036 A275037 * A275039 A275040 A275041

Keyword

nonn

Author

R. H. Hardin, Jul 14 2016

Status

approved