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 A220559 Number of ways to reciprocally link elements of an n X 5 array either to themselves or to exactly one horizontal or antidiagonal neighbor. 1
 8, 149, 2604, 45966, 810778, 14298089, 252139015, 4446314533, 78407942556, 1382674335890, 24382584703194, 429971411669361, 7582273047532603, 133708574584054949, 2357865880743076540, 41579468847568886038 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 5 of A220562. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 21*a(n-1) - 62*a(n-2) + 47*a(n-3) - 5*a(n-4) for n>5. Empirical g.f.: x*(8 - 19*x - 29*x^2 + 144*x^3 - 23*x^4) / ((1 - x)*(1 - 20*x + 42*x^2 - 5*x^3)). - Colin Barker, Jul 31 2018 EXAMPLE Some solutions for n=3 0=self 3=ne 4=w 6=e 7=sw (reciprocal directions total 10): ..0..0..0..6..4....0..0..0..6..4....0..0..0..6..4....0..0..6..4..0 ..6..4..0..6..4....0..6..4..0..0....0..6..4..7..0....0..7..7..7..0 ..0..6..4..0..0....0..6..4..0..0....0..0..3..0..0....3..3..3..0..0 CROSSREFS Cf. A220562. Sequence in context: A244028 A075351 A302063 * A264642 A300872 A217502 Adjacent sequences:  A220556 A220557 A220558 * A220560 A220561 A220562 KEYWORD nonn AUTHOR R. H. Hardin, Dec 16 2012 STATUS approved

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Last modified January 26 11:13 EST 2020. Contains 331279 sequences. (Running on oeis4.)