OFFSET
1,1
COMMENTS
This is the case h = 2 of the h-perfect numbers as defined in the Harborth link.
LINKS
Heiko Harborth, On h-perfect numbers, Annales Mathematicae et Informaticae, 41 (2013) pp. 57-62.
FORMULA
EXAMPLE
10 is a term since sigma(10) + sigma(20) = 60, that is 6*10.
MATHEMATICA
Select[Range[10^7], DivisorSigma[1, #] + DivisorSigma[1, 2 #] == 6 # &] (* Michael De Vlieger, Feb 04 2017 *)
PROG
(PARI) isok(n, h=2) = sigma(n) + sigma(h*n) == 2*n*(h+1);
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Feb 04 2017
EXTENSIONS
More terms from Jinyuan Wang, Feb 11 2020
STATUS
approved