OFFSET
1,2
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
FORMULA
a(n) ~ (Pi^2/12) * n^2. - Amiram Eldar, Oct 21 2020
EXAMPLE
The first squarefree numbers are: 1, 2, 3, 5, 6, 7, 10, ...
So, the first partial sums are: 1, 3, 6, 11, 17, 24, 34, ...
MATHEMATICA
Accumulate[Select[Range[100], SquareFreeQ]] (* Harvey P. Dale, Jan 09 2016 *)
PROG
(PARI) lista(nn)=s = 0; for (n=1, nn, if (issquarefree(n), s += n; print1(s, ", "); ); ); \\ Michel Marcus, Oct 01 2015
(PARI) helper(n, k)=my(t=(n+1)\k); binomial(t, 2)*k + (n+1 - t*k)*t
a(n)=my(s); forsquarefree(k=1, sqrtint(n), s+=moebius(k)*helper(n, k[1]^2)); s \\ Charles R Greathouse IV, Feb 05 2018
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Feb 10 2010
STATUS
approved