OFFSET
1,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..10000 (first 520 terms from Reinhard Zumkeller)
FORMULA
a(n) = |Sum_{i=1..n} sqrt(mu(i))|^2. - Enrique Pérez Herrero, Jul 30 2012
EXAMPLE
n mu(n) ... n: 1 2 3 4 5 6 7 8
- ------ .... |---------------->
1 .. +1 ..... | + - - 0 - + - 0
2 .. -1 ..... | - + + 0 + - + 0
3 .. -1 ..... | - + + 0 + - + 0
4 ... 0 ..... | 0 0 0 0 0 0 0 0
5 .. -1 ..... | - + + 0 + - + 0 a(8)=20, as there are
6 .. +1 ..... | + - - 0 - + - 0 20 '+1's in the 8x8-square
7 .. -1 ..... | - + + 0 + - + 0 (represented as '+')
8 ... 0 ..... | 0 0 0 0 0 0 0 0.
MATHEMATICA
Table[Abs[Sum[Sqrt[MoebiusMu[i]], {i, 1, n}]]^2, {n, 60}] (* Enrique Pérez Herrero, Jul 30 2012 *)
PROG
(Haskell)
a081240 n = length [() | u <- [1..n], v <- [1..n],
a008683 u * a008683 v == 1]
-- Reinhard Zumkeller, Aug 03 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Mar 11 2003
STATUS
approved