OFFSET
1,8
COMMENTS
A078147 gives run lengths in this sequence, apart from initial run of zeros. - Reinhard Zumkeller, Apr 22 2012
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
a(n)=sum_{1<p^2<=n} phi(p)trunc(n/p^2) where phi is Euler's phi function and trunc is the greatest integer function.
EXAMPLE
a(24)=12 as the sequences counted are 1,2,4; 2,4,8; 3,6,12; 4,8,16; 5,10,20; 6,12,24; 1,3,9; 2,6,18; 4,6,9; 8,12,18; 1,4,16; 9,12,16
MAPLE
sum(numtheory[phi](p)*trunc(n/p^2), p=2..trunc(sqrt(n)));
PROG
(Haskell)
a132345 n = sum $ zipWith (*)
(tail a000010_list) (map ((div n) . (^ 2)) [2..a000196 n])
-- Reinhard Zumkeller, Apr 22 2012
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
David Angell (angell(AT)maths.unsw.edu.au), Nov 07 2007
STATUS
approved