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A220734
Number of ways to reciprocally link elements of an nX4 array either to themselves or to exactly two horizontal, diagonal and antidiagonal neighbors, without consecutive collinear links
1
1, 13, 103, 712, 5760, 45421, 355883, 2807273, 22112517, 174154372, 1371967416, 10807412577, 85133340257, 670628304993, 5282781003159, 41614380864876, 327811678257588, 2582291933091677, 20341654064411427, 160238619700892677
OFFSET
1,2
COMMENTS
Column 4 of A220738
LINKS
FORMULA
Empirical: a(n) = 9*a(n-1) -4*a(n-2) -23*a(n-3) -153*a(n-4) +204*a(n-5) +564*a(n-6) -700*a(n-7) +95*a(n-8) +2061*a(n-9) -3000*a(n-10) -4459*a(n-11) +2151*a(n-12) +5800*a(n-13) +320*a(n-14) -1276*a(n-15) -925*a(n-16) +233*a(n-17) +48*a(n-18) +13*a(n-19) -a(n-20)
EXAMPLE
Some solutions for n=3 0=self 1=nw 3=ne 4=w 6=e 7=sw 9=se (reciprocal directions total 10)
.00.69.49.00...00.69.49.00...00.69.47.00...00.67.49.00...69.47.00.00
.00.00.17.17...69.47.16.14...00.39.16.47...36.47.67.14...39.16.47.00
.00.36.34.00...36.14.00.00...00.00.13.00...36.34.00.00...00.13.00.00
CROSSREFS
Sequence in context: A119594 A066034 A228213 * A268991 A216179 A240804
KEYWORD
nonn
AUTHOR
R. H. Hardin Dec 18 2012
STATUS
approved