A270052 - OEIS

A270052

Number of nX2 0..4 arrays with some element plus some horizontally or vertically adjacent neighbor totalling four exactly once.

5, 240, 5400, 99840, 1683240, 26891280, 414705720, 6237722400, 92095515720, 1340308323120, 19283874244440, 274868623748160, 3887609470141800, 54625048810247760, 763245268612477560, 10612743734992545120

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Column 2 of A270058.

LINKS

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

FORMULA

Empirical: a(n) = 26*a(n-1) -169*a(n-2) for n>3.

Empirical: g.f. 5*x -120*x^2*(-2+7*x) / (13*x-1)^2 . - R. J. Mathar, Mar 09 2016

EXAMPLE

Some solutions for n=4

..3..3. .1..0. .2..3. .1..4. .2..0. .3..3. .4..4. .1..2. .4..4. .4..1

..3..2. .1..3. .0..0. .2..3. .3..0. .2..2. .1..4. .2..0. .1..3. .2..0

..0..3. .4..4. .3..1. .0..0. .4..0. .4..4. .4..2. .1..2. .1..2. .1..2

..1..3. .2..4. .3..0. .2..4. .4..2. .3..2. .3..1. .1..2. .4..4. .3..3

CROSSREFS

Cf. A270058.

Sequence in context: A140518 A269551 A200962 * A174767 A230885 A142732

Adjacent sequences: A270049 A270050 A270051 * A270053 A270054 A270055

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 09 2016

STATUS

approved

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