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A068416 Number of partitionings of n X n checkerboard into two edgewise-connected sets. 2
0, 6, 53, 627, 16213, 1123743, 221984391, 127561384993, 215767063451331, 1082828220389781579, 16209089366362071416785, 726438398002211876667379681, 97741115155002465272674416929195, 39565596445488219947994403962984729307 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

One of the partitions may completely surround the other. (Cf. A271802) - Andrew Howroyd, Apr 14 2016

LINKS

Table of n, a(n) for n=1..14.

FORMULA

a(n) = A271802(n) + A140517(n-2). - Andrew Howroyd, Apr 14 2016

EXAMPLE

Illustration of a(2)=6:

   11   12   12   12   11   11

   22   12   22   11   12   21

Illustration of a few solutions of a(3):

   111   112   122   111   111

   121   111   112   212   111

   111   111   222   222   222

CROSSREFS

Cf. A068392, A271802, A068381, A068417, A113900.

Sequence in context: A185148 A243921 A109092 * A221413 A145003 A248369

Adjacent sequences:  A068413 A068414 A068415 * A068417 A068418 A068419

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 02 2002

EXTENSIONS

a(7)-a(14) from Andrew Howroyd, Apr 14 2016

STATUS

approved

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Last modified August 19 20:20 EDT 2019. Contains 326133 sequences. (Running on oeis4.)