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 A220629 Number of ways to reciprocally link elements of an n X 5 array either to themselves or to exactly two horizontal or antidiagonal neighbors. 1
 1, 8, 44, 257, 1481, 8560, 49448, 285669, 1650333, 9534128, 55079528, 318199485, 1838267585, 10619840324, 61351790884, 354434918989, 2047603011865, 11829190267612, 68338316351600, 394796716945057, 2280776817922653 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Column 5 of A220632. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 4*a(n-1) + 9*a(n-2) + 7*a(n-3) + 2*a(n-4) - a(n-5). Empirical g.f.: x*(1 + 3*x - x^2)*(1 + x + x^2) / ((1 + x)*(1 - 5*x - 4*x^2 - 3*x^3 + x^4)). - Colin Barker, Aug 01 2018 EXAMPLE Some solutions for n=3 0=self 3=ne 4=w 6=e 7=sw (reciprocal directions total 10): .00.67.46.46.47...00.67.46.47.00...00.00.00.00.00...00.00.67.46.47 .36.47.00.36.47...36.46.34.67.47...00.67.46.47.00...00.37.67.34.00 .36.46.46.34.00...00.00.36.34.00...36.46.34.00.00...36.34.00.00.00 CROSSREFS Cf. A220632. Sequence in context: A147828 A155604 A126476 * A210118 A112908 A264819 Adjacent sequences:  A220626 A220627 A220628 * A220630 A220631 A220632 KEYWORD nonn AUTHOR R. H. Hardin, Dec 17 2012 STATUS approved

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Last modified October 29 18:49 EDT 2020. Contains 338067 sequences. (Running on oeis4.)