A207026 - OEIS

A207026

Number of 3Xn 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 0 1 and 1 0 1 vertically

6, 36, 90, 252, 624, 1350, 3025, 6256, 12788, 25792, 50630, 99012, 190920, 365041, 694038, 1309524, 2460150, 4599952, 8565768, 15899422, 29415965, 54278252, 99908040, 183482116, 336298170, 615243752, 1123669472, 2049072321, 3731220822

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Row 3 of A207024

LINKS

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

FORMULA

Empirical: a(n) = 3*a(n-1) +a(n-2) -5*a(n-3) -10*a(n-4) +12*a(n-5) +11*a(n-6) +a(n-7) -15*a(n-8) +a(n-9) -7*a(n-10) +3*a(n-11) +3*a(n-12) +9*a(n-13) -4*a(n-14) -2*a(n-16) -a(n-18) +a(n-19)

EXAMPLE

Some solutions for n=4

..1..0..0..1....0..1..0..1....0..0..1..0....1..1..1..0....1..1..0..0

..0..1..0..0....0..1..0..1....1..0..1..0....0..0..1..0....1..1..1..1

..0..1..0..0....0..1..0..1....0..0..1..0....0..0..1..0....1..1..0..0

CROSSREFS

Sequence in context: A152746 A207363 A207600 * A207171 A207454 A213189

Adjacent sequences: A207023 A207024 A207025 * A207027 A207028 A207029

KEYWORD

nonn

AUTHOR

R. H. Hardin Feb 14 2012

STATUS

approved