A222942 - OEIS

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A222942

Number of n X 4 0..4 arrays with no element equal to another at a city block distance of exactly two, and new values 0..4 introduced in row major order.

7, 273, 5880, 130680, 2883000, 63772920, 1409319480, 31155452280, 688658403000, 15222762787320, 336492918625080, 7438082253365880, 164416380693123000, 3634373283904809720, 80336675486923162680, 1775817062973868911480

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OFFSET

1,1

COMMENTS

Column 4 of A222944.

LINKS

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

FORMULA

Empirical: a(n) = 17*a(n-1) + 136*a(n-2) -512*a(n-3) for n>5.

Empirical g.f.: x*(7 + 154*x + 287*x^2 - 2824*x^3 + 1536*x^4) / ((1 + 8*x)*(1 - 25*x + 64*x^2)). - Colin Barker, Aug 16 2018

EXAMPLE

Some solutions for n=3: