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A220592 Number of ways to reciprocally link elements of an nX4 array either to themselves or to exactly two king-move neighbors 1
1, 155, 6156, 308246, 14637699, 702811381, 33667621356, 1613595307718, 77327320807492, 3705787367955871, 177593105803460322, 8510833856676985632, 407866501681469579790, 19546273938797565641009, 936720274971414734673655 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 4 of A220595

LINKS

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

FORMULA

Empirical: a(n) = 40*a(n-1) +395*a(n-2) -769*a(n-3) +2095*a(n-4) -16049*a(n-5) -71697*a(n-6) -119950*a(n-7) +1037497*a(n-8) -139363*a(n-9) -1979661*a(n-10) +1507756*a(n-11) +1041993*a(n-12) -2247051*a(n-13) +1215317*a(n-14) -16637*a(n-15) -311055*a(n-16) +67983*a(n-17) +54951*a(n-18) -4355*a(n-19) -9884*a(n-20) +766*a(n-21) +683*a(n-22) -103*a(n-23) -9*a(n-24) +2*a(n-25)

EXAMPLE

Some solutions for n=3 0=self 1=nw 2=n 3=ne 4=w 6=e 7=sw 8=s 9=se (reciprocal directions total 10)

.00.68.47.00...69.47.89.00...69.46.46.48...89.67.48.00...00.67.46.47

.89.23.69.47...36.14.26.14...00.18.78.28...23.17.28.00...39.67.34.78

.26.14.36.14...00.00.00.00...00.23.26.24...36.46.24.00...36.14.36.24

CROSSREFS

Sequence in context: A110834 A110842 A289300 * A278730 A278432 A299829

Adjacent sequences:  A220589 A220590 A220591 * A220593 A220594 A220595

KEYWORD

nonn

AUTHOR

R. H. Hardin Dec 16 2012

STATUS

approved

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Last modified June 19 00:55 EDT 2019. Contains 324217 sequences. (Running on oeis4.)