OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
Rafael Jakimczuk and Matilde Lalín, Asymptotics of sums of divisor functions over sequences with restricted factorization structure, Notes on Number Theory and Discrete Mathematics, Vol. 28, No. 4 (2022), pp. 617-634, eq. (7).
FORMULA
MATHEMATICA
DivisorSigma[1, Select[Range[10^4], # == 1 || Min[FactorInteger[#][[;; , 2]]] > 2 &]]
PROG
(PARI) lista(kmax) = for(k = 1, kmax, if(k==1 || vecmin(factor(k)[, 2]) > 2, print1(sigma(k), ", ")));
(Python)
from itertools import count, islice
from math import prod
from sympy import factorint
def A362986_gen(): # generator of terms
for n in count(1):
f = factorint(n)
if all(e>2 for e in f.values()):
yield prod((p**(e+1)-1)//(p-1) for p, e in f.items())
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, May 12 2023
STATUS
approved