OFFSET
1,1
COMMENTS
LINKS
Ivan Neretin, Table of n, a(n) for n = 1..10000
FORMULA
Sum_{k=1..n} a(k) ~ c * n^2 / 2, where c = 3 - zeta(2) = 1.355065... . - Amiram Eldar, Mar 25 2024
EXAMPLE
For n=4, 3n=12, sum of divisors of n is 1+2+4=7, so a(4)=12-7=5.
MAPLE
with(numtheory): for n from 1 to 150 do printf(`%d, `, 3*n-sigma(n)) od:
MATHEMATICA
Table[3 n - DivisorSigma[1, n], {n, 70}] (* Ivan Neretin, Sep 30 2017 *)
PROG
(PARI) a(n)=3*n-sigma(n) \\ Charles R Greathouse IV, Mar 16 2016
CROSSREFS
KEYWORD
sign,easy
AUTHOR
EXTENSIONS
More terms from James A. Sellers, Jun 01 2000
STATUS
approved