OFFSET
1,2
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..1000
FORMULA
a(n) ~ Pi^2 * n^2 / (12*Zeta(3)). - Vaclav Kotesovec, Jan 11 2019
MATHEMATICA
Accumulate@ Table[DivisorSum[n, # &, CoprimeQ[#, n/#] &], {n, 52}] (* Michael De Vlieger, Mar 18 2017 *)
PROG
(PARI) usigma(n)= { local(f, s=1); f=factor(n); for(i=1, matsize(f)[1], s*=1 + f[i, 1]^f[i, 2]); return(s) }
{ a=0; for (n=1, 1000, a+=usigma(n); write("b064609.txt", n, " ", a) ) } \\ Harry J. Smith, Sep 20 2009
(Python)
from sympy.ntheory.factor_ import udivisor_sigma
def a(n): return sum(udivisor_sigma(j, 1) for j in range(1, n + 1))
print([a(n) for n in range(1, 101)]) # Indranil Ghosh, Mar 18 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Sep 24 2001
STATUS
approved