OFFSET
1,2
COMMENTS
n divides a(n) for n = 1, 21, 333592, ...
FORMULA
a(p) = 2*(p+1) for p = primes (A000040).
EXAMPLE
a(6) = tau(1)*pod(1) + tau(2)*pod(2) + tau(3)*pod(3) + tau(6)*pod(6) = (1*1) + (2*2) + (2*3) + (4*36) = 155.
PROG
(Magma) [&+[# [c: c in Divisors(d)] * &*[c: c in Divisors(d)]: d in Divisors(n)]: n in [1..100]]
(PARI) a(n) = sumdiv(n, d, my(dd=divisors(d)); #dd*vecprod(dd)); \\ Michel Marcus, Apr 25 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Apr 25 2019
STATUS
approved