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, 25, 201, 2024, 21380, 220299, 2316754, 24198121, 253601977, 2654925237, 27806859021, 291197368229, 3049635082130, 31937451907839, 334468779079214, 3502756567542222, 36682984009174381, 384166287213883140

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