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%I #7 Feb 07 2016 21:40:55
%S 1,1,7,13,19,31,43,61,85,97,121,151,175,211,241,271,313,349,385,439,
%T 499,535,583,649,691,757,823,877,955,1027,1087,1159,1249,1321,1401,
%U 1483,1561,1663,1765,1827,1945,2053,2133,2233,2347,2443,2563,2677,2779,2905
%N Number of unit hexagonal lattice cells (hexagon in the origin) enclosed by origin centered circle of radius n.
%C As n -> infinity, lim a(n)/(n^2) -> 2*Pi/(3*sqrt(3)).
%Y Cf. A053458, A267710.
%Y Cf. A248897(2*Pi/(3*sqrt(3))).
%K nonn,easy
%O 1,3
%A _Luca Petrone_, Jan 20 2016
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