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A267803 Number of unit hexagonal lattice cells (hexagon in the origin) enclosed by origin centered circle of radius n. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

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

LINKS

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

CROSSREFS

Cf. A053458, A267710.

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

Sequence in context: A172057 A173176 A216550 * A240971 A023255 A122482

Adjacent sequences:  A267800 A267801 A267802 * A267804 A267805 A267806

KEYWORD

nonn,easy

AUTHOR

Luca Petrone, Jan 20 2016

STATUS

approved

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Last modified July 28 04:28 EDT 2021. Contains 346317 sequences. (Running on oeis4.)