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A220712 Number of ways to reciprocally link elements of an 7Xn array either to themselves or to exactly two horizontal and antidiagonal neighbors, without consecutive collinear links 1
1, 1, 21, 129, 932, 6412, 44976, 311193, 2168111, 15034974, 104478616, 725286308, 5037269200, 34977393156, 242898931716, 1686719471828, 11713075485508, 81338093590180, 564832581201972, 3922330554994484, 27237632538545092 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Row 7 of A220708

LINKS

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

FORMULA

Empirical: a(n) = a(n-1) +76*a(n-2) -4*a(n-3) -2156*a(n-4) -520*a(n-5) +32432*a(n-6) +9800*a(n-7) -296352*a(n-8) -80128*a(n-9) +1755472*a(n-10) +365536*a(n-11) -6970672*a(n-12) -1003248*a(n-13) +18839680*a(n-14) +1679040*a(n-15) -34716928*a(n-16) -1650048*a(n-17) +43135744*a(n-18) +820736*a(n-19) -35163136*a(n-20) -61440*a(n-21) +17813504*a(n-22) -116736*a(n-23) -5017600*a(n-24) +36864*a(n-25) +589824*a(n-26) for n>32

EXAMPLE

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

.00.67.47...00.00.00...00.00.00...00.67.47...00.67.47...00.67.47...00.00.00

.36.34.00...00.00.00...00.67.47...36.34.00...36.34.00...36.34.00...00.00.00

.00.00.00...00.67.47...36.34.00...00.67.47...00.67.47...00.67.47...00.67.47

.00.00.00...36.34.00...00.00.00...36.34.00...36.34.00...36.34.00...36.34.00

.00.00.00...00.00.00...00.67.47...00.00.00...00.00.00...00.67.47...00.00.00

.00.00.00...00.00.00...36.34.00...00.67.47...00.00.00...36.34.00...00.67.47

.00.00.00...00.00.00...00.00.00...36.34.00...00.00.00...00.00.00...36.34.00

CROSSREFS

Sequence in context: A317265 A213565 A041852 * A295916 A124117 A219926

Adjacent sequences:  A220709 A220710 A220711 * A220713 A220714 A220715

KEYWORD

nonn

AUTHOR

R. H. Hardin Dec 18 2012

STATUS

approved

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Last modified January 19 15:13 EST 2022. Contains 350466 sequences. (Running on oeis4.)