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 A220549 Number of ways to reciprocally link elements of an nX4 array either to themselves or to exactly one horizontal, vertical or antidiagonal neighbor 1
 5, 108, 1814, 32173, 565061, 9943416, 174911750, 3077034244, 54130248568, 952245176313, 16751640356635, 294690365449276, 5184113807856060, 91197538858856819, 1604322628219475789, 28222813114190945744 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 4 of A220553 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 11*a(n-1) +111*a(n-2) +127*a(n-3) -649*a(n-4) -981*a(n-5) +1615*a(n-6) +2067*a(n-7) -2349*a(n-8) -1177*a(n-9) +1383*a(n-10) +199*a(n-11) -337*a(n-12) +3*a(n-13) +31*a(n-14) -a(n-15) -a(n-16) EXAMPLE Some solutions for n=3 0=self 2=n 3=ne 4=w 6=e 7=sw 8=s (reciprocal directions total 10) ..6..4..7..8....0..0..6..4....6..4..7..7....8..8..0..7....6..4..7..7 ..0..3..0..2....0..7..0..8....0..3..3..0....2..2..3..0....0..3..3..0 ..6..4..6..4....3..0..0..2....6..4..0..0....0..0..0..0....6..4..6..4 CROSSREFS Sequence in context: A142479 A204110 A113056 * A210904 A048564 A139971 Adjacent sequences:  A220546 A220547 A220548 * A220550 A220551 A220552 KEYWORD nonn AUTHOR R. H. Hardin Dec 15 2012 STATUS approved

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Last modified August 17 22:32 EDT 2018. Contains 313817 sequences. (Running on oeis4.)