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A278357 Number of n X 2 0..1 arrays with rows and columns in lexicographic nondecreasing order but with exactly one mistake. 1
1, 6, 27, 96, 281, 708, 1590, 3264, 6237, 11242, 19305, 31824, 50661, 78248, 117708, 172992, 249033, 351918, 489079, 669504, 903969, 1205292, 1588610, 2071680, 2675205, 3423186, 4343301, 5467312, 6831501, 8477136, 10450968, 12805760 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

FORMULA

Empirical: a(n) = (1/5040)*n^7 + (1/240)*n^6 + (31/720)*n^5 + (1/16)*n^4 + (41/360)*n^3 + (13/30)*n^2 + (12/35)*n.

Conjectures from Colin Barker, Feb 09 2019: (Start)

G.f.: x*(1 - 2*x + 7*x^2 - 8*x^3 + 3*x^4) / (1 - x)^8.

a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>8.

(End)

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Column 2 of A278363.

Sequence in context: A341385 A344100 A136747 * A001940 A320049 A121591

Adjacent sequences:  A278354 A278355 A278356 * A278358 A278359 A278360

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 19 2016

STATUS

approved

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Last modified June 28 21:04 EDT 2022. Contains 354907 sequences. (Running on oeis4.)