OFFSET
1,2
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 1..10000
FORMULA
Ramanujan's asymptotic formula: (5/6)*Zeta(3)*n^3+O(n^2*log(n)^2)
MAPLE
A072379 := proc(n)
add( numtheory[sigma](k)^2, k=0..n) ;
end proc:
seq(A072379(n), n=1..80) ; # R. J. Mathar, Jul 09 2024
MATHEMATICA
Accumulate[Table[DivisorSigma[1, k]^2, {k, 1, 50}]] (* Vaclav Kotesovec, Sep 10 2018 *)
PROG
(PARI) a(n) = sum(k=1, n, sigma(k)^2) \\ Michel Marcus, Jun 20 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), Jul 20 2002
STATUS
approved