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A238822 Number of equilateral triangles bounded by the sides and diagonals of a regular 3n-gon. 1

%I

%S 1,14,69,188,465,882,1645,2648,4257,6170,9273,12564,17485,22778,30585,

%T 38288,50031,61074,77311,91580,114009,134750,164634,192456

%N Number of equilateral triangles bounded by the sides and diagonals of a regular 3n-gon.

%H Antreas Hatzipolakis and Giovanni Resta, <a href="http://list.seqfan.eu/pipermail/seqfan/2013-April/011012.html">Number of Equilateral Triangles in Regular 3n-gon</a>, Postings to the Sequence Fans Mailing List, Apr 08 2013

%H Giovanni Resta, <a href="/A238822/a238822.png">Illustration for a(3) = 69</a>

%Y Cf. A006561.

%K nonn,nice,more

%O 1,2

%A _N. J. A. Sloane_, Mar 07 2014

%E a(6)-a(24) from _Luca Petrone_, Mar 28 2017

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Last modified November 11 22:31 EST 2019. Contains 329046 sequences. (Running on oeis4.)