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A184542
Number of (n+2) X 5 binary arrays with each 3 X 3 subblock having rows and columns in lexicographically nondecreasing order.
1
147, 340, 631, 1048, 1627, 2413, 3461, 4837, 6619, 8898, 11779, 15382, 19843, 25315, 31969, 39995, 49603, 61024, 74511, 90340, 108811, 130249, 155005, 183457, 216011, 253102, 295195, 342786, 396403, 456607, 523993, 599191, 682867, 775724, 878503
OFFSET
1,1
COMMENTS
Column 3 of A184548.
LINKS
FORMULA
Empirical: a(n) = (1/120)*n^5 + (5/24)*n^4 + (49/24)*n^3 + (739/24)*n^2 + (1659/20)*n + 31.
Conjectures from Colin Barker, Apr 13 2018: (Start)
G.f.: x*(147 - 542*x + 796*x^2 - 578*x^3 + 209*x^4 - 31*x^5) / (1 - x)^6.
a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>5.
(End)
EXAMPLE
Some solutions for 4 X 5:
..0..0..0..0..0....0..0..0..0..1....0..0..0..0..0....0..0..0..0..0
..0..0..0..1..1....0..0..0..0..1....0..0..0..1..1....0..0..0..0..1
..0..0..1..0..0....0..0..1..1..1....0..1..1..0..0....0..0..1..1..0
..0..0..1..1..1....0..1..1..1..1....1..1..1..1..1....0..1..1..1..0
CROSSREFS
Cf. A184548.
Sequence in context: A325608 A375155 A255103 * A350638 A162701 A063701
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 16 2011
STATUS
approved