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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
1, 13, 48, 298, 1520, 8338, 44976, 244029, 1322551, 7171769, 38885648, 210854845, 1143330649, 6199601829, 33616711696, 182283373322, 988413912488, 5359579124490, 29061800830768, 157584813722329, 854488462716575 (list; graph; refs; listen; history; text; internal format)
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

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Last modified February 2 19:29 EST 2023. Contains 360024 sequences. (Running on oeis4.)