A267710 Number of unit triangular lattice cells enclosed by origin centered circle of diameter n.

0, 6, 6, 24, 24, 54, 60, 96, 114, 150, 180, 216, 258, 324, 348, 426, 450, 540, 564, 666, 720, 804, 870, 954, 1056, 1134, 1230, 1344, 1416, 1542, 1614, 1752, 1842, 1974, 2100, 2208, 2346, 2478, 2628, 2778, 2898, 3084, 3180, 3378, 3474, 3684, 3822, 4002, 4176, 4356

Offset: 1

Author

Luca Petrone, Jan 19 2016

Keywords

• easy
• nonn

Comments

As n -> infinity, lim a(n)/(n^2) -> Pi/sqrt(3).

Links

• Luca Petrone, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A093602 (Pi/sqrt(3)).