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A220602 T(n,k)=Number of ways to reciprocally link elements of an nXk array either to themselves or to exactly two horizontal, vertical and antidiagonal neighbors, without 3-loops 7
1, 1, 1, 1, 2, 1, 1, 7, 7, 1, 1, 17, 65, 17, 1, 1, 44, 471, 471, 44, 1, 1, 117, 3469, 9047, 3469, 117, 1, 1, 305, 25747, 167614, 167614, 25747, 305, 1, 1, 798, 190425, 3174778, 7558495, 3174778, 190425, 798, 1, 1, 2091, 1408823, 60138423, 352586943 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

Table starts

.1.....1..........1...............1...................1

.1.....2..........7..............17..................44

.1.....7.........65.............471................3469

.1....17........471............9047..............167614

.1....44.......3469..........167614.............7558495

.1...117......25747.........3174778...........352586943

.1...305.....190425........60138423.........16505365334

.1...798....1408823......1137615308........770615995060

.1..2091...10424813.....21523535122......35978245868462

.1..5473...77135267....407249783145....1680090131446571

.1.14328..570740149...7705461280893...78453960278374893

.1.37513.4223043591.145792738613760.3663456651896335065

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..180

EXAMPLE

Some solutions for n=3 k=4 0=self 2=n 3=ne 4=w 6=e 7=sw 8=s (reciprocal directions total 10)

.00.68.48.78...00.68.48.00...00.00.67.47...00.67.47.00...00.67.47.00

.68.24.23.28...68.24.28.00...00.38.36.48...36.34.67.47...38.37.68.48

.26.46.46.24...26.46.24.00...00.26.46.24...00.36.34.00...23.00.26.24

CROSSREFS

Column 2 is A108479

Sequence in context: A122021 A303817 A158200 * A166345 A015110 A128596

Adjacent sequences:  A220599 A220600 A220601 * A220603 A220604 A220605

KEYWORD

nonn,tabl

AUTHOR

R. H. Hardin Dec 16 2012

STATUS

approved

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Last modified May 14 07:13 EDT 2021. Contains 343879 sequences. (Running on oeis4.)