OFFSET
1,4
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..10000
FORMULA
(1/3!)*(sigma[1](n)^3-3*sigma[1](n)*sigma[2](n)+2*sigma[3](n)).
MAPLE
a:= n-> coeff(expand(mul(1+d*x, d=numtheory[divisors](n))), x, 3):
seq(a(n), n=1..100); # Alois P. Heinz, Mar 18 2023
PROG
(PARI) a(n) = 1/6*(sigma(n, 1)^3 - 3*sigma(n, 1)*sigma(n, 2) + 2*sigma(n, 3)) \\ Michel Marcus, Jun 17 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladeta Jovovic, Feb 08 2002
STATUS
approved