OFFSET
1,4
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harry J. Smith)
FORMULA
Sum_{k=1..n} a(k) ~ (5*zeta(3)/6 - Pi^2/18) * n^3. - Amiram Eldar, Apr 01 2024
MATHEMATICA
a[n_] := Module[{s = DivisorSigma[1, n]}, s*(s - n - 1)]; a[1] = 0; Array[a, 100] (* Amiram Eldar, Apr 01 2024 *)
PROG
(PARI) a(n) = {my(s = sigma(n)); if(n == 1, 0, s*(s-n-1)); }
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jason Earls, Jul 18 2001
EXTENSIONS
a(1) corrected by Amiram Eldar, Apr 01 2024
STATUS
approved