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A220710 Number of ways to reciprocally link elements of an 5 X n array either to themselves or to exactly two horizontal and antidiagonal neighbors, without consecutive collinear links. 1
1, 1, 8, 28, 107, 405, 1520, 5706, 21418, 80390, 301736, 1132543, 4250895, 15955408, 59887275, 224782132, 843701335, 3166765105, 11886195940, 44613876758, 167454575870, 628527215306, 2359126067724, 8854788952291, 33235734276043 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Row 5 of A220708.

LINKS

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

FORMULA

Empirical: a(n) = 3*a(n-1) + 7*a(n-2) - 14*a(n-3) - 11*a(n-4) + 17*a(n-5) + 5*a(n-6) - 6*a(n-7) for n>11.

Empirical g.f.: x*(1 - 2*x - 2*x^2 + 11*x^3 - 8*x^4 - 6*x^5 + 14*x^6 - 18*x^7 - 3*x^8 + 18*x^9 - 8*x^10) / ((1 - x)*(1 + x)*(1 - 3*x - 6*x^2 + 11*x^3 + 5*x^4 - 6*x^5)). - Colin Barker, Aug 02 2018

EXAMPLE

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

.00.00.00...00.00.00...00.67.47...00.67.47...00.00.00...00.00.00...00.00.00

.00.67.47...00.00.00...36.34.00...36.34.00...00.00.00...00.67.47...00.00.00

.36.34.00...00.00.00...00.00.00...00.00.00...00.67.47...36.34.00...00.00.00

.00.00.00...00.67.47...00.00.00...00.67.47...36.34.00...00.67.47...00.00.00

.00.00.00...36.34.00...00.00.00...36.34.00...00.00.00...36.34.00...00.00.00

CROSSREFS

Cf. A220708.

Sequence in context: A153365 A317149 A316879 * A260935 A289608 A317607

Adjacent sequences:  A220707 A220708 A220709 * A220711 A220712 A220713

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 18 2012

STATUS

approved

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Last modified May 6 09:45 EDT 2021. Contains 343580 sequences. (Running on oeis4.)