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A204032 Number of (n+1) X 2 0..1 arrays with the sums of 2 X 2 subblocks nondecreasing rightwards and downwards. 4
16, 44, 121, 286, 676, 1482, 3249, 6840, 14400, 29640, 61009, 123994, 252004, 508526, 1026169, 2062468, 4145296, 8312988, 16670889, 33390774, 66879684, 133865682, 267944161, 536117488, 1072693504, 2145878288, 4292739361, 8586527026 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 1 of A204039.

LINKS

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

FORMULA

Empirical: a(n) = 4*a(n-1) -18*a(n-3) +17*a(n-4) +22*a(n-5) -36*a(n-6) +20*a(n-8) -8*a(n-9).

Empirical g.f.: x*(16 - 20*x - 55*x^2 + 90*x^3 + 52*x^4 - 144*x^5 + 20*x^6 + 72*x^7 - 32*x^8) / ((1 - x)^3*(1 + x)*(1 - 2*x)*(1 - 2*x^2)^2). - Colin Barker, Feb 20 2018

EXAMPLE

Some solutions for n=4:

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

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

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

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

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

CROSSREFS

Cf. A204039.

Sequence in context: A258547 A211573 A211582 * A192143 A221593 A300962

Adjacent sequences:  A204029 A204030 A204031 * A204033 A204034 A204035

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 09 2012

STATUS

approved

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Last modified December 9 19:51 EST 2019. Contains 329879 sequences. (Running on oeis4.)