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A223950 Number of 3 X n 0..1 arrays with diagonals and antidiagonals unimodal and rows nondecreasing. 1
8, 27, 54, 96, 157, 241, 352, 494, 671, 887, 1146, 1452, 1809, 2221, 2692, 3226, 3827, 4499, 5246, 6072, 6981, 7977, 9064, 10246, 11527, 12911, 14402, 16004, 17721, 19557, 21516, 23602, 25819, 28171, 30662, 33296, 36077, 39009, 42096, 45342, 48751, 52327 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 3 of A223949.

LINKS

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

FORMULA

Empirical: a(n) = (2/3)*n^3 + (3/2)*n^2 + (41/6)*n + 2 for n>1.

Conjectures from Colin Barker, Aug 24 2018: (Start)

G.f.: x*(8 - 5*x - 6*x^2 + 10*x^3 - 3*x^4) / (1 - x)^4.

a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>5.

(End)

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Cf. A223949.

Sequence in context: A122013 A250230 A250278 * A131620 A141227 A224134

Adjacent sequences:  A223947 A223948 A223949 * A223951 A223952 A223953

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 29 2013

STATUS

approved

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Last modified November 15 19:18 EST 2019. Contains 329149 sequences. (Running on oeis4.)