4,2

Table of n, a(n) for n=4..60.

Wikipedia, Regular polygons

Kival Ngaokrajang, Illustration of initial terms

a(n) = Round(n/(4*tan(Pi/n)).

a(5) = 5 because a(1) is a square and a(5) is a regular octagon with sides equal to 1 which has a rounded area of 5.

(PARI) a(n) = round(n / (4*tan(Pi/n))); \\ Michel Marcus, Sep 04 2013

Sequence in context: A050418 A011869 A177738 * A226189 A235592 A100054

Adjacent sequences: A134027 A134028 A134029 * A134031 A134032 A134033

easy,nonn

Ben Paul Thurston, Jan 11 2008

approved