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A222890 Number of n X 1 0..7 arrays with no element equal to another at a city block distance of exactly two, and new values 0..7 introduced in row major order. 1
1, 2, 3, 7, 20, 67, 255, 1080, 5016, 25249, 136289, 780658, 4696002, 29374011, 189373083, 1248978556, 8376922028, 56874440053, 389553674037, 2685020105574, 18589701176694, 129115803986575, 898809701733551, 6266899328414512 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 1 of A222894.

LINKS

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

FORMULA

Empirical: a(n) = 22*a(n-1) - 190*a(n-2) + 820*a(n-3) - 1849*a(n-4) + 2038*a(n-5) - 840*a(n-6) for n>8.

Empirical g.f.: x*(1 + x)*(1 - 21*x + 170*x^2 - 669*x^3 + 1314*x^4 - 1157*x^5 + 309*x^6) / ((1 - x)*(1 - 2*x)*(1 - 3*x)*(1 - 4*x)*(1 - 5*x)*(1 - 7*x)). - Colin Barker, Aug 16 2018

EXAMPLE

All solutions for n=3:

..0....0....0

..0....1....1

..1....1....2

CROSSREFS

Cf. A222894.

Sequence in context: A222939 A222867 A222776 * A011968 A080021 A306666

Adjacent sequences:  A222887 A222888 A222889 * A222891 A222892 A222893

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 08 2013

STATUS

approved

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Last modified January 26 07:27 EST 2022. Contains 350576 sequences. (Running on oeis4.)