Sigma {numbers} | R Documentation |
Divisor Functions
Description
Sum of powers of all divisors of a natural number.
Usage
Sigma(n, k = 1, proper = FALSE)
tau(n)
Arguments
n |
Positive integer. |
k |
Numeric scalar, the exponent to be used. |
proper |
Logical; if |
Details
Total sum of all integer divisors of 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
.
Value
Natural number, the number or sum of all divisors.
Note
Works well up to 10^9
.
References
https://en.wikipedia.org/wiki/Divisor_function
https://en.wikipedia.org/wiki/Ramanujan_tau_function
See Also
Examples
sapply(1:16, Sigma, k = 0)
sapply(1:16, Sigma, k = 1)
sapply(1:16, Sigma, proper = TRUE)
[Package numbers version 0.8-5 Index]