OFFSET
1,1
COMMENTS
This sequence will contain terms of the form 7*P, where P is a perfect number (A000396) not divisible by 7. Proof: sigma(7*P)/(7*P) = sigma(7)*sigma(P)/(7*P) = 8*(2*P)/(7*P) = 16/7. QED
LINKS
G. P. Michon, Multiperfect Numbers and Hemiperfect Numbers
Walter Nissen, Abundancy: Some Resources (preliminary version 4)
EXAMPLE
544635 is a term, since sigma(544635)/544635 = 1244880/544635 = 16/7.
MATHEMATICA
Select[Range[5*10^8], DivisorSigma[1, #]/# == 16/7 &]
Do[If[DivisorSigma[1, k]/k == 16/7, Print[k]], {k, 5*10^8}]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Timothy L. Tiffin, Aug 20 2021
EXTENSIONS
a(8)-a(9) from Michel Marcus, Aug 21 2021
STATUS
approved