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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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Peter Kagey, Table of n, a(n) for n = 1..1000 Code Golf Stack Exchange, Concentric rings on a snub square tiling. Index entries for linear recurrences with constant coefficients, signature (2,-1). 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 Adjacent sequences: A332016 A332017 A332018 * A332020 A332021 A332022 KEYWORD easy,nonn AUTHOR Peter Kagey, Feb 04 2020 STATUS approved

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Last modified November 29 18:13 EST 2022. Contains 358431 sequences. (Running on oeis4.)