A217949 - OEIS

A217949

Number of n-element 0..3 arrays with each element the minimum of 3 adjacent elements of a random 0..3 array of n+2 elements.

4, 16, 50, 130, 310, 736, 1821, 4673, 12107, 31103, 79039, 199819, 505477, 1282309, 3259549, 8288613, 21064316, 53497376, 135833020, 344914900, 875983319, 2224986219, 5651490601, 14354263713, 36457137516, 92593166734, 235168023403

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OFFSET

1,1

COMMENTS

See A217954 and A228461 for more information. - N. J. A. Sloane, Sep 02 2013

LINKS

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

FORMULA

Empirical: a(n) = 4*a(n-1) -6*a(n-2) +4*a(n-3) +5*a(n-4) -4*a(n-5) +6*a(n-6) +4*a(n-7) +2*a(n-9) +a(n-10).

Empirical: G.f.: -x*(x^3+x^2+2) *(x^6+2*x^5+x^4+4*x^3+4*x^2+2) / ( (x^5+3*x^2-2*x+1) *(x^5+2*x^4+x^2+2*x-1) ). - R. J. Mathar, May 17 2014

EXAMPLE

Some solutions for n=4

..2....0....1....0....1....0....0....0....0....2....2....3....1....2....1....1

..0....3....2....0....1....2....0....2....2....3....2....3....2....2....3....1

..0....0....1....2....1....3....2....2....2....2....2....2....2....3....1....1

..0....0....0....3....0....0....2....1....0....1....0....1....2....2....0....3

CROSSREFS

Column 3 of A217954. Cf. A217883, A217954.

Sequence in context: A217952 A217951 A217950 * A227675 A345325 A203094

Adjacent sequences: A217946 A217947 A217948 * A217950 A217951 A217952

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 15 2012

STATUS

approved