OFFSET
1,3
LINKS
Eric Weisstein's World of Mathematics, Equilateral Triangle
Wikipedia, Equilateral triangle
FORMULA
PROG
(PARI) a(n)=sqrtint(3*n^2\4) \\ Charles R Greathouse IV, Jan 06 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Reinhard Zumkeller, Jan 20 2010
STATUS
approved