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A183905 Number of nondecreasing arrangements of n+2 numbers in 0..2 with each number being the sum mod 3 of two others. 1
1, 4, 10, 17, 25, 34, 44, 55, 67, 80, 94, 109, 125, 142, 160, 179, 199, 220, 242, 265, 289, 314, 340, 367, 395, 424, 454, 485, 517, 550, 584, 619, 655, 692, 730, 769, 809, 850, 892, 935, 979, 1024, 1070, 1117, 1165, 1214, 1264, 1315, 1367, 1420, 1474, 1529, 1585 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 2 of A183912.

LINKS

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

FORMULA

Empirical: a(n) = (1/2)*n^2 + (7/2)*n - 5 for n>1.

a(n) = Triangular number(A000217)-11.

Conjectures from Colin Barker, Apr 05 2018: (Start)

G.f.: x*(1 + x + x^2 - 2*x^3) / (1 - x)^3.

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>4.

(End)

EXAMPLE

Some solutions for n=4:

..0....0....1....0....1....0....0....0....0....0....0....0....1....0....0....0

..1....0....1....1....1....1....0....0....1....0....0....0....1....0....0....0

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

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

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

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

MATHEMATICA

Abs[Table[n (n + 1)/2 - 11, {n, 4, 200}]] (* Vladimir Joseph Stephan Orlovsky, Jun 12 2011 *)

CROSSREFS

Cf. A000217, A183912.

Sequence in context: A310541 A246394 A310542 * A301288 A009860 A294249

Adjacent sequences:  A183902 A183903 A183904 * A183906 A183907 A183908

KEYWORD

nonn,easy

AUTHOR

R. H. Hardin, Jan 07 2011

STATUS

approved

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Last modified February 28 11:08 EST 2020. Contains 332323 sequences. (Running on oeis4.)