OFFSET
1,2
LINKS
Eric Weisstein's World of Mathematics, Lens
FORMULA
a(n) = floor((4*Pi - 3*sqrt(3))/6*n^2).
EXAMPLE
a(2) = 4 because a lens given by the intersection of two circles of radius two has an area of approximately 4.91347...
MATHEMATICA
Table[Floor[(4*Pi - 3*Sqrt[3])/6*r^2], {r, 1, 60}]
PROG
(PARI) a(n)=(4*Pi-sqrt(27))*n^2\6 \\ Charles R Greathouse IV, Nov 27 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Joseph Biberstine (jrbibers(AT)indiana.edu), Jan 16 2005
STATUS
approved