OFFSET
1,1
LINKS
Graeme L. Cohen and H. J. J. te Riele, Iterating the sum-of-divisors function, Exp. Math., 5 (1996), 91-100.
MAPLE
with(numtheory):
P := proc (q)
local n, result:
result := []:
for n to q do
if sigma(sigma(2*n)) = 2*sigma(sigma(n)) then
result := [op(result), n]:
end if
end do:
print(result):
end proc:
P(10^3);
MATHEMATICA
Select[Range[800], DivisorSigma[1, DivisorSigma[1, 2#]]==2DivisorSigma[1, DivisorSigma[1, #]]&] (* Stefano Spezia, Jun 05 2024 *)
PROG
(Python)
from sympy import divisor_sigma as sigma
def P(q):
result = []
for n in range(1, q + 1):
if sigma(sigma(2 * n)) == 2 * sigma(sigma(n)):
result.append(n)
print(result)
P(10**3)
CROSSREFS
KEYWORD
nonn
AUTHOR
Rafik Khalfi, Jun 04 2024
STATUS
approved