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A220677 Number of ways to reciprocally link elements of an nX4 array either to themselves or to exactly two horizontal, vertical and antidiagonal neighbors, without consecutive collinear links 1
1, 25, 201, 2024, 21380, 220299, 2316754, 24198121, 253601977, 2654925237, 27806859021, 291197368229, 3049635082130, 31937451907839, 334468779079214, 3502756567542222, 36682984009174381, 384166287213883140 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 4 of A220681

LINKS

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

FORMULA

Empirical: a(n) = 98*a(n-2) +346*a(n-3) -1613*a(n-4) -8977*a(n-5) +5505*a(n-6) +86304*a(n-7) +59970*a(n-8) -357044*a(n-9) -486590*a(n-10) +666046*a(n-11) +1441907*a(n-12) -238170*a(n-13) -2087126*a(n-14) -1250313*a(n-15) +1268690*a(n-16) +2309710*a(n-17) +379003*a(n-18) -1537142*a(n-19) -1091082*a(n-20) +131004*a(n-21) +567626*a(n-22) +329248*a(n-23) -5235*a(n-24) -112357*a(n-25) -60445*a(n-26) -11850*a(n-27) -94*a(n-28) +168*a(n-29) -a(n-30)

EXAMPLE

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

.68.47.67.47...00.00.78.00...00.00.00.00...00.00.00.78...68.47.68.48

.23.38.36.47...00.36.24.00...68.48.00.00...00.78.36.24...23.00.27.27

.00.26.34.00...00.00.00.00...26.24.00.00...36.24.00.00...00.36.34.00

CROSSREFS

Sequence in context: A146738 A146722 A042210 * A125362 A126520 A324794

Adjacent sequences:  A220674 A220675 A220676 * A220678 A220679 A220680

KEYWORD

nonn

AUTHOR

R. H. Hardin Dec 17 2012

STATUS

approved

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Last modified October 3 08:29 EDT 2022. Contains 357231 sequences. (Running on oeis4.)