OFFSET
1,9
COMMENTS
Also, the number of integers k in {1,2,...,n-1} such that k*n is square. - John W. Layman, Sep 08 2011
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
a(72)=5 since (2,12,72), (8,24,72), (18,36,72), (32,48,72), (50,60,72) are the possible three term geometric progressions.
PROG
(Haskell)
a057918 n = sum $ map ((0 ^) . (`mod` n) . (^ 2)) [1..n-1]
-- Reinhard Zumkeller, Mar 27 2012
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Henry Bottomley, Nov 22 2000
STATUS
approved