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A220681 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 consecutive collinear links 7
1, 1, 1, 1, 4, 1, 1, 9, 9, 1, 1, 25, 43, 25, 1, 1, 64, 201, 201, 64, 1, 1, 169, 968, 2024, 968, 169, 1, 1, 441, 4604, 21380, 21380, 4604, 441, 1, 1, 1156, 22000, 220299, 468036, 220299, 22000, 1156, 1, 1, 3025, 104976, 2316754, 9973284, 9973284, 2316754 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

Table starts

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

.1.....4........9...........25...............64.................169

.1.....9.......43..........201..............968................4604

.1....25......201.........2024............21380..............220299

.1....64......968........21380...........468036.............9973284

.1...169.....4604.......220299..........9973284...........455249977

.1...441....22000......2316754........215926776.........21051034046

.1..1156...104976.....24198121.......4649097520........969333059888

.1..3025...501096....253601977.....100274426148......44710643494095

.1..7921..2391737...2654925237....2161781726064....2061425679292684

.1.20736.11415981..27806859021...46610315291176...95053260696179636

.1.54289.54489429.291197368229.1004947894341776.4382893797173364311

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)

.00.00.00.00...00.00.00.00...68.48.00.00...00.00.00.78...00.67.47.00

.68.48.68.48...00.68.47.00...26.24.68.48...00.78.36.24...38.38.00.00

.26.24.26.24...00.23.00.00...00.00.26.24...36.24.00.00...26.24.00.00

CROSSREFS

Column 2 is A007598(n+1)

Sequence in context: A146767 A146955 A155451 * A189280 A168621 A039756

Adjacent sequences:  A220678 A220679 A220680 * A220682 A220683 A220684

KEYWORD

nonn,tabl

AUTHOR

R. H. Hardin Dec 17 2012

STATUS

approved

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Last modified May 13 14:30 EDT 2021. Contains 343859 sequences. (Running on oeis4.)