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A334706 Number of collinear triples in a 4 X n rectangular grid. 2
4, 8, 20, 44, 84, 140, 224, 332, 472, 648, 864, 1120, 1428, 1784, 2196, 2668, 3204, 3804, 4480, 5228, 6056, 6968, 7968, 9056, 10244, 11528, 12916, 14412, 16020, 17740, 19584, 21548, 23640, 25864, 28224, 30720, 33364, 36152, 39092, 42188, 45444, 48860, 52448, 56204 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
From Stefano Spezia, Jun 20 2020: (Start)
G.f.: 4*x*(1 + x^2 + 2*x^3 + 2*x^4)/((1 - x)^4*(1 + 2*x + 2*x^2 + x^3)).
a(n) = 2*a(n-1) - a(n-3) - a(n-4) + 2*a(n-6) - a(n-7) for n > 7. (End)
CROSSREFS
A column of A334704.
Sequence in context: A254128 A047196 A009889 * A095804 A084219 A190589
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 13 2020
EXTENSIONS
Terms a(8) and beyond from Giovanni Resta, Jun 20 2020
STATUS
approved

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Last modified May 22 13:22 EDT 2024. Contains 372755 sequences. (Running on oeis4.)