A220707 Number of ways to reciprocally link elements of an n X 7 array either to themselves or to exactly two horizontal and antidiagonal neighbors, without consecutive collinear links.

1, 13, 48, 298, 1520, 8338, 44976, 244029, 1322551, 7171769, 38885648, 210854845, 1143330649, 6199601829, 33616711696, 182283373322, 988413912488, 5359579124490, 29061800830768, 157584813722329, 854488462716575

Offset

1,2

Comments

Column 7 of A220708.

Links

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

Formula

Empirical: a(n) = 5*a(n-1) +6*a(n-2) -17*a(n-3) -19*a(n-4) +10*a(n-5) +16*a(n-6) -46*a(n-7) +7*a(n-8) +15*a(n-9) -14*a(n-10) +21*a(n-11) +3*a(n-12) +10*a(n-13) +8*a(n-14) +2*a(n-15) +5*a(n-16) +a(n-17) +2*a(n-18) -a(n-19) -a(n-20).

Example

Some solutions for n=3 0=self 3=ne 4=w 6=e 7=sw (reciprocal directions total 10)
.00.00.00.00.00.00.00...00.00.00.00.00.00.00...00.67.47.00.00.00.00
.00.00.67.47.00.00.00...00.00.67.47.67.47.00...36.34.00.00.00.67.47
.00.36.34.00.00.00.00...00.36.34.36.34.00.00...00.00.00.00.36.34.00

Crossrefs

Cf. A220708.

Sequence in context: A027980 A200254 A288746 * A189349 A013200 A156694

Adjacent sequences: A220704 A220705 A220706 * A220708 A220709 A220710

Keyword

nonn

Author

R. H. Hardin, Dec 18 2012

Status

approved