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A220727 Number of ways to reciprocally link elements of an 3Xn array either to themselves or to exactly two horizontal, diagonal or antidiagonal neighbors 1
1, 4, 30, 230, 1819, 14466, 114900, 913187, 7256380, 57664692, 458236178, 3641435760, 28937067889, 229951848995, 1827338913535, 14521161884614, 115394100670410, 916992651769082, 7286988782183320, 57906904219355630 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 3 of A220725

LINKS

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

FORMULA

Empirical: a(n) = 5*a(n-1) +24*a(n-2) -a(n-3) -25*a(n-4) -33*a(n-5) +10*a(n-6) +19*a(n-7) +4*a(n-8) -4*a(n-9) -a(n-10)

EXAMPLE

Some solutions for n=3 0=self 1=nw 3=ne 4=w 6=e 7=sw 9=se (reciprocal directions total 10)

.69.49.00...00.69.47...00.67.47...69.47.00...00.79.00...00.67.47...00.69.47

.69.14.17...00.36.14...36.34.00...39.16.47...39.67.14...39.37.00...00.37.17

.00.13.00...00.00.00...00.00.00...00.13.00...36.14.00...36.14.00...36.34.00

CROSSREFS

Sequence in context: A084976 A000313 A082144 * A137971 A346579 A300159

Adjacent sequences:  A220724 A220725 A220726 * A220728 A220729 A220730

KEYWORD

nonn

AUTHOR

R. H. Hardin Dec 18 2012

STATUS

approved

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Last modified October 17 06:54 EDT 2021. Contains 348048 sequences. (Running on oeis4.)