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A220722 Number of ways to reciprocally link elements of an nX5 array either to themselves or to exactly two horizontal, diagonal or antidiagonal neighbors 1
1, 68, 1819, 52189, 1485872, 42378036, 1208447287, 34459871148, 982649830527, 28021037742705, 799042082604660, 22785317589182003, 649741368852004381, 18527889499243277120, 528337436670523419632, 15065960264863439367995 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 5 of A220725

LINKS

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

FORMULA

Empirical: a(n) = 24*a(n-1) +104*a(n-2) +571*a(n-3) +3582*a(n-4) +7794*a(n-5) +4788*a(n-6) -16926*a(n-7) -90288*a(n-8) -168845*a(n-9) -84443*a(n-10) +109179*a(n-11) +193126*a(n-12) +248993*a(n-13) +425415*a(n-14) +384428*a(n-15) +353459*a(n-16) +31964*a(n-17) -136170*a(n-18) -85703*a(n-19) -29195*a(n-20) +14155*a(n-21) +6903*a(n-22) +243*a(n-23) -252*a(n-24) -25*a(n-25)

EXAMPLE

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

.69.47.69.46.47...69.47.00.69.47...00.69.46.46.47...00.69.46.49.00

.39.19.00.13.00...39.16.47.36.14...00.69.14.37.00...00.00.16.46.14

.00.16.14.00.00...00.13.00.00.00...00.00.13.00.00...00.00.00.00.00

CROSSREFS

Sequence in context: A230687 A231106 A228332 * A017784 A035802 A035729

Adjacent sequences:  A220719 A220720 A220721 * A220723 A220724 A220725

KEYWORD

nonn

AUTHOR

R. H. Hardin Dec 18 2012

STATUS

approved

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Last modified January 29 14:07 EST 2020. Contains 331338 sequences. (Running on oeis4.)