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A332019
The number of cells added in the n-th generation of the following procedure: start by coloring any triangle on the snub square tiling, then repeatedly color every cell that shares a vertex with a colored cell.
1
1, 9, 21, 35, 48, 60, 72, 84, 96, 108, 120, 132, 144, 156, 168, 180, 192, 204, 216, 228, 240, 252, 264, 276, 288, 300, 312, 324, 336, 348, 360, 372, 384, 396, 408, 420, 432, 444, 456, 468, 480, 492, 504, 516, 528, 540, 552, 564, 576, 588, 600, 612, 624, 636
OFFSET
1,2
FORMULA
a(n) = 12*(n - 1) for n > 4.
From Stefano Spezia, Feb 05 2020: (Start)
G.f.: x*(1 + 7*x + 4*x^2 + 2*x^3 - x^4 - x^5)/(-1 + x)^2.
a(n) = 2*a(n-1) - a(n-2) for n > 6.
(End)
CROSSREFS
Cf. A008594.
A296368 is the analogous sequence when instead coloring every cell that shares a side with a colored cell.
Sequence in context: A253052 A043112 A043892 * A146069 A140673 A186294
KEYWORD
easy,nonn
AUTHOR
Peter Kagey, Feb 04 2020
STATUS
approved