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A055582
Sixth column of triangle A055252.
7
1, 9, 48, 198, 699, 2223, 6562, 18324, 49029, 126837, 319332, 786258, 1900351, 4521771, 10616598, 24641280, 56622825, 128974545, 291503800, 654311070, 1459617411, 3238002279, 7147093578, 15703473708, 34359737869, 74893491693
OFFSET
0,2
LINKS
Robert Davis, Greg Simay, Further Combinatorics and Applications of Two-Toned Tilings, arXiv:2001.11089 [math.CO], 2020.
FORMULA
G.f.: 1/(((1-2*x)^3)*(1-x)^3).
a(n)= A055252(n+5, 5). a(n)= sum(a(j), j=0..n-1)+A034009(n), n >= 1.
a(n)= (n^2 - 3*n + 8)*(2^(n+3) -1)/2 - 9*(n+3). [Yahia Kahloune, Aug 11 2013]
MATHEMATICA
CoefficientList[Series[1/(((1 - 2 x)^3) (1 - x)^3), {x, 0, 25}], x] (* Michael De Vlieger, Apr 23 2020 *)
CROSSREFS
Cf. A055252, A055249, A034009, partial sums of A055581.
Sequence in context: A212107 A073979 A018984 * A359175 A054460 A115053
KEYWORD
easy,nonn
AUTHOR
Wolfdieter Lang, May 26 2000
STATUS
approved