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A189807 Number of right triangles on an (n+1) X 3 grid. 1
14, 44, 94, 158, 238, 330, 434, 550, 678, 818, 970, 1134, 1310, 1498, 1698, 1910, 2134, 2370, 2618, 2878, 3150, 3434, 3730, 4038, 4358, 4690, 5034, 5390, 5758, 6138, 6530, 6934, 7350, 7778, 8218, 8670, 9134, 9610, 10098, 10598, 11110, 11634, 12170, 12718 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Column 2 of A189814.
LINKS
FORMULA
Empirical: a(n) = 6*n^2 + 26*n - 42 for n>3.
Conjectures from Colin Barker, May 03 2018: (Start)
G.f.: 2*x*(7 + x + 2*x^2 - 3*x^3 + x^4 - 2*x^5) / (1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>6.
(End)
EXAMPLE
Some solutions for n=3:
..3..0....0..1....2..1....1..1....2..0....3..0....1..1....2..2....0..0....3..1
..0..0....0..0....1..0....0..1....2..1....2..0....0..2....1..1....0..2....1..1
..3..1....3..1....3..0....1..2....3..0....3..2....2..2....3..1....3..0....3..2
CROSSREFS
Cf. A189814.
Sequence in context: A089031 A265152 A033587 * A009942 A031130 A215199
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 28 2011
STATUS
approved

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Last modified May 25 02:39 EDT 2024. Contains 372782 sequences. (Running on oeis4.)