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A200155 Number of 0..n arrays x(0..3) of 4 elements with zero 3rd differences. 2
4, 9, 22, 41, 66, 107, 158, 219, 304, 403, 516, 661, 824, 1005, 1226, 1469, 1734, 2047, 2386, 2751, 3172, 3623, 4104, 4649, 5228, 5841, 6526, 7249, 8010, 8851, 9734, 10659, 11672, 12731, 13836, 15037, 16288, 17589, 18994, 20453, 21966, 23591, 25274, 27015 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 4 of A200154.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = 2*a(n-1) - a(n-2) + 2*a(n-3) - 4*a(n-4) + 2*a(n-5) - a(n-6) + 2*a(n-7) - a(n-8).

Empirical g.f.: x*(4 + x + 8*x^2 - 2*x^3 + 4*x^4 + 2*x^6 - x^7) / ((1 - x)^4*(1 + x + x^2)^2). - Colin Barker, Mar 02 2018

EXAMPLE

Some solutions for n=6:

..3....4....2....0....0....4....4....3....3....3....2....2....6....3....5....3

..3....4....6....4....1....1....5....1....0....0....2....2....1....4....1....4

..4....3....6....6....3....0....4....1....0....1....3....2....1....4....0....3

..6....1....2....6....6....1....1....3....3....6....5....2....6....3....2....0

CROSSREFS

Cf. A200154.

Sequence in context: A158140 A290647 A105314 * A002835 A253289 A032288

Adjacent sequences:  A200152 A200153 A200154 * A200156 A200157 A200158

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 13 2011

STATUS

approved

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Last modified September 26 05:00 EDT 2020. Contains 337346 sequences. (Running on oeis4.)