
sigma(n, k = 1, proper = FALSE)tau(n)
TRUE
, n will not be considered
as a divisor of itself; default: FALSE.n
to the power of k
,
including 1
and n
. For k=0
this is the number of divisors, for k=1
it is the sum of all divisors of n
.
tau
is Ramanujan`s tau function, here computed using
sigma(., 5)
and sigma(., 11)
.
A number is called refactorable, if tau(n)
divides n
,
for example n=12
or n=18
.
http://en.wikipedia.org/wiki/Divisor_function
http://en.wikipedia.org/wiki/Tau-function
factorize
sapply(1:16, sigma, k = 0)
sapply(1:16, sigma, k = 1)
sapply(1:16, sigma, proper = TRUE)
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