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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 Giovanni Resta, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (2,0,-1,-1,0,2,-1). 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 Adjacent sequences: A334703 A334704 A334705 * A334707 A334708 A334709 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.)