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A245989 Number of length n+2 0..2 arrays with no pair in any consecutive three terms totalling exactly 2. 1
8, 12, 18, 26, 38, 56, 82, 120, 176, 258, 378, 554, 812, 1190, 1744, 2556, 3746, 5490, 8046, 11792, 17282, 25328, 37120, 54402, 79730, 116850, 171252, 250982, 367832, 539084, 790066, 1157898, 1696982, 2487048, 3644946, 5341928, 7828976, 11473922 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = a(n-1) + a(n-3).

Empirical g.f.: 2*x*(4 + 2*x + 3*x^2) / (1 - x - x^3). - Colin Barker, Nov 05 2018

EXAMPLE

Some solutions for n=10:

  0  1  0  1  1  0  2  2  0  2  0  2  0  0  0  1

  0  2  1  2  0  0  1  2  1  1  0  2  0  0  1  2

  0  2  0  2  0  1  2  1  0  2  0  2  0  0  0  2

  0  2  0  1  0  0  2  2  0  2  1  1  1  1  0  1

  0  1  1  2  0  0  2  2  0  2  0  2  0  0  0  2

  0  2  0  2  1  1  2  1  1  1  0  2  0  0  0  2

  0  2  0  2  0  0  1  2  0  2  0  2  0  0  1  2

  0  2  0  2  0  0  2  2  0  2  0  2  0  0  0  2

  0  1  1  2  1  1  2  1  0  2  0  1  1  0  0  1

  0  2  0  1  0  0  2  2  0  2  0  2  0  0  0  2

  0  2  0  2  0  0  2  2  0  1  1  2  0  0  0  2

  0  2  0  2  1  0  1  1  0  2  0  1  0  0  1  2

CROSSREFS

Column 2 of A245995.

Sequence in context: A157940 A308494 A087696 * A293529 A028393 A066681

Adjacent sequences:  A245986 A245987 A245988 * A245990 A245991 A245992

KEYWORD

nonn

AUTHOR

R. H. Hardin, Aug 09 2014

STATUS

approved

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Last modified March 28 05:38 EDT 2020. Contains 333073 sequences. (Running on oeis4.)