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 A216987 Number of city-block distance 1, pressure limit 2 movements in an nX4 array with each element moving exactly one horizontally or vertically, no element acquiring more than two neighbors, and without 2-loops 1
 0, 80, 4794, 280900, 15836932, 886416182, 49491906456, 2761454361344, 154047246448662, 8592994055896310, 479322218408145970, 26736736612809407136, 1491380920762839897984, 83189511828057155698994 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Column 4 of A216991 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 84*a(n-1) -1756*a(n-2) +9538*a(n-3) +41862*a(n-4) -461584*a(n-5) +1025726*a(n-6) +76920*a(n-7) -2075057*a(n-8) +1315158*a(n-9) +48430*a(n-10) +125844*a(n-11) -68128*a(n-12) +6896*a(n-13) -7808*a(n-14) +780*a(n-15) -4*a(n-16) EXAMPLE Some solutions for n=3 (movement: 0=n 1=e 2=s 3=w) ..1..1..2..3....1..1..2..3....2..3..1..2....2..3..3..3....2..3..3..2 ..1..0..1..0....0..3..3..0....1..0..2..3....2..3..0..2....1..0..3..3 ..0..3..1..0....1..1..1..0....0..3..1..0....1..1..0..3....0..1..0..0 CROSSREFS Sequence in context: A247861 A203171 A076004 * A283102 A259076 A190931 Adjacent sequences:  A216984 A216985 A216986 * A216988 A216989 A216990 KEYWORD nonn AUTHOR R. H. Hardin Sep 21 2012 STATUS approved

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Last modified October 22 22:34 EDT 2019. Contains 328335 sequences. (Running on oeis4.)