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A251213 Number of (n+1)X(2+1) 0..1 arrays with no 2X2 subblock having zero or two 1s 1
21, 63, 191, 589, 1807, 5569, 17119, 52713, 162143, 499081, 1535535, 4725689, 14541087, 44748169, 137696911, 423732505, 1303909887, 4012461097, 12347225455, 37995389753, 116920467935, 359791896905, 1107162729807, 3406999063641 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A251219

LINKS

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

FORMULA

Empirical: a(n) = 3*a(n-1) +4*a(n-2) -12*a(n-3) +4*a(n-5).

Empirical: G.f.: -x*(21-82*x^2+16*x^3+32*x^4) / ( -1+3*x+4*x^2-12*x^3+4*x^5 ). - R. J. Mathar, May 12 2016

EXAMPLE

Some solutions for n=4

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

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

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

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

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

CROSSREFS

Sequence in context: A082060 A025525 A033850 * A170930 A113622 A069215

Adjacent sequences:  A251210 A251211 A251212 * A251214 A251215 A251216

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 30 2014

STATUS

approved

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Last modified September 21 13:37 EDT 2019. Contains 327253 sequences. (Running on oeis4.)