A267803 Number of unit hexagonal lattice cells (hexagon in the origin) enclosed by origin centered circle of radius n.

1, 1, 7, 13, 19, 31, 43, 61, 85, 97, 121, 151, 175, 211, 241, 271, 313, 349, 385, 439, 499, 535, 583, 649, 691, 757, 823, 877, 955, 1027, 1087, 1159, 1249, 1321, 1401, 1483, 1561, 1663, 1765, 1827, 1945, 2053, 2133, 2233, 2347, 2443, 2563, 2677, 2779, 2905

Offset

1,3

Links

Table of n, a(n) for n=1..50.

Nicolay Avilov, Illustration of the first terms

Formula

Limit_{n->oo} a(n)/(n^2) = 2*Pi/(3*sqrt(3)).

Crossrefs

Cf. A053458, A267710.

Cf. A248897 (2*Pi/(3*sqrt(3))).

Sequence in context: A172057 A173176 A216550 * A240971 A023255 A373584

Adjacent sequences: A267800 A267801 A267802 * A267804 A267805 A267806

Keyword

nonn,easy

Author

Luca Petrone, Jan 20 2016

Status

approved