OFFSET
1,1
LINKS
Max Alekseyev, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Centered Polygonal Number
FORMULA
a(n) = -1 for n in A166259.
a(n) = 1 for n = k^2-1.
CROSSREFS
KEYWORD
sign
AUTHOR
Alexander Adamchuk, Apr 26 2007
EXTENSIONS
Edited and b-file provided by Max Alekseyev, Jan 20 2010
STATUS
approved