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A208639 Number of 4 X n 0..1 arrays with new values 0..1 introduced in row major order and no element equal to more than one of its immediate leftward or upward or right-upward antidiagonal neighbors. 1
8, 34, 95, 225, 494, 1042, 2149, 4375, 8840, 17784, 35687, 71509, 143170, 286510, 573209, 1146627, 2293484, 4587220, 9174715, 18349729, 36699782, 73399914, 146800205, 293600815, 587202064, 1174404592, 2348809679, 4697619885 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 4 of A208637.

LINKS

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

FORMULA

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

Conjectures from Colin Barker, Jul 05 2018: (Start)

G.f.: x*(8 - 6*x - 3*x^2 + 2*x^4) / ((1 - x)^3*(1 - 2*x)).

a(n) = (-42 + 35*2^n - 13*n - n^2) / 2 for n>1.

(End)

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Cf. A208637.

Sequence in context: A249743 A298140 A301887 * A240785 A066804 A033455

Adjacent sequences:  A208636 A208637 A208638 * A208640 A208641 A208642

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 29 2012

STATUS

approved

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Last modified February 16 21:59 EST 2019. Contains 320200 sequences. (Running on oeis4.)