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, 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

R. H. Hardin, Table of n, a(n) for n = 1..210

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

Adjacent sequences: A220731 A220732 A220733 * A220735 A220736 A220737

Keyword

nonn

Author

R. H. Hardin Dec 18 2012

Status

approved