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A212776 Half the number of 0..2 arrays of length n+2 with second differences nonzero 1
11, 27, 66, 162, 397, 973, 2385, 5846, 14329, 35122, 86088, 211011, 517211, 1267741, 3107372, 7616509, 18668898, 45759514, 112161581, 274920321, 673859821, 1651704234, 4048508001, 9923336574, 24323184920, 59618790539, 146132186103 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A212782

LINKS

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

FORMULA

Empirical: a(n) = a(n-1) +2*a(n-2) +3*a(n-3) +2*a(n-4).

Empirical: G.f. -x*(11+16*x+17*x^2+9*x^3) / ( -1+x+2*x^2+3*x^3+2*x^4 ). - R. J. Mathar, Jul 01 2013

EXAMPLE

Some solutions for n=5

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

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

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

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

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

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

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

CROSSREFS

Sequence in context: A106839 A044072 A044453 * A137019 A122929 A030756

Adjacent sequences:  A212773 A212774 A212775 * A212777 A212778 A212779

KEYWORD

nonn

AUTHOR

R. H. Hardin May 27 2012

STATUS

approved

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Last modified December 5 03:59 EST 2021. Contains 349530 sequences. (Running on oeis4.)