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A245945 Number of length n+3 0..2 arrays with some pair in every consecutive four terms totalling exactly 2. 1
71, 197, 545, 1501, 4145, 11441, 31577, 87161, 240581, 664051, 1832917, 5059221, 13964475, 38544783, 106391413, 293661867, 810566283, 2237327253, 6175476757, 17045567707, 47049222251, 129865390965, 358454804639, 989407924729 (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) = 2*a(n-1) + 2*a(n-2) + a(n-3) - a(n-4) - 2*a(n-5) - 2*a(n-6) - a(n-7) + a(n-8) + a(n-9).

Empirical g.f.: x*(71 + 55*x + 9*x^2 - 54*x^3 - 73*x^4 - 57*x^5 - 15*x^6 + 36*x^7 + 27*x^8) / ((1 - x)*(1 - x - 3*x^2 - 4*x^3 - 3*x^4 - x^5 + x^6 + 2*x^7 + x^8)). - Colin Barker, Nov 05 2018

EXAMPLE

Some solutions for n=8:

..0....1....1....1....2....1....0....0....1....1....2....1....0....0....1....2

..1....1....2....1....0....2....2....1....0....2....0....0....0....1....1....0

..2....2....0....2....1....0....2....0....2....2....0....1....2....1....0....0

..0....1....0....0....1....1....0....2....0....1....2....2....0....0....1....1

..1....2....1....1....1....0....2....1....0....0....2....1....1....2....1....2

..0....1....1....0....1....1....2....0....1....1....0....0....0....2....1....1

..2....2....1....2....2....1....1....0....1....2....2....1....1....1....2....0

..2....0....1....2....1....0....0....1....0....2....0....0....2....0....1....2

..0....1....0....0....2....0....1....1....0....0....2....2....0....2....2....0

..0....1....1....1....0....2....1....2....2....2....2....1....2....0....1....0

..2....2....1....1....0....2....2....1....2....1....1....0....0....0....2....2

CROSSREFS

Column 2 of A245950.

Sequence in context: A142808 A101110 A142893 * A166255 A142076 A096698

Adjacent sequences:  A245942 A245943 A245944 * A245946 A245947 A245948

KEYWORD

nonn

AUTHOR

R. H. Hardin, Aug 08 2014

STATUS

approved

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Last modified January 17 17:18 EST 2021. Contains 340247 sequences. (Running on oeis4.)