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A209367 Number of n X 1 1..3 arrays with no element with value z exactly a city block distance of z from another element with value z. 1
3, 8, 19, 35, 64, 110, 185, 322, 599, 1084, 1902, 3280, 5816, 10425, 18711, 33023, 58229, 102865, 183340, 326023, 578770, 1023268, 1814036, 3218397, 5719285, 10142300, 17984603, 31872737, 56560901, 100345791, 178058874, 315719677 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 1 of A209374.

LINKS

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

FORMULA

Empirical: a(n) = a(n-2) + 4*a(n-4) + 4*a(n-5) + 5*a(n-6) - a(n-7) - 5*a(n-8) - 5*a(n-9) - 5*a(n-10) + a(n-11) + 2*a(n-12) for n>14.

Empirical g.f.: x*(3 + 8*x + 16*x^2 + 27*x^3 + 33*x^4 + 31*x^5 - 2*x^6 - 41*x^7 - 54*x^8 - 35*x^9 - 12*x^10 - 11*x^11 - 9*x^12 - 2*x^13) / ((1 - x)*(1 + x - 4*x^4 - 8*x^5 - 13*x^6 - 12*x^7 - 7*x^8 - 2*x^9 + 3*x^10 + 2*x^11)). - Colin Barker, Jul 09 2018

EXAMPLE

All solutions for n=5:

..2....1....2....3....3....2....3....3....3....2....1....2....3....3

..3....3....1....3....2....1....1....1....2....3....2....3....1....3

..1....1....3....1....3....3....2....2....2....3....2....1....2....1

..2....2....3....2....1....3....2....1....1....2....3....2....2....2

..1....1....2....2....3....1....1....3....3....2....3....2....3....1

CROSSREFS

Cf. A209374.

Sequence in context: A184444 A139020 A147358 * A086167 A083186 A055341

Adjacent sequences:  A209364 A209365 A209366 * A209368 A209369 A209370

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 07 2012

STATUS

approved

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Last modified October 28 21:20 EDT 2020. Contains 338064 sequences. (Running on oeis4.)