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, 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

Author

Peter Kagey, Feb 04 2020

Keywords

• easy
• nonn

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).

Crossrefs

Cf. A008594.

A296368 is the analogous sequence when instead coloring every cell that shares a side with a colored cell.

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)