OFFSET
1,1
COMMENTS
For the first 26 terms, the quotient (sigma(n)/phi(n)) is 2 or 3.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..7901 (terms below 6.5*10^14, calculated using data from Jud McCranie)
MAPLE
with(numtheory); BNM7:=[]: for z from 1 to 1 do for m from 1 to 1000000 do n:=12*m+7; if sigma(n) mod phi(n) = 0 then BNM7:=[op(BNM7), n] fi; od; od; BNM7;
MATHEMATICA
Select[Range[10^7], Mod[#, 12] == 7 && Divisible[DivisorSigma[1, #], EulerPhi[#]] &] (* Amiram Eldar, Dec 04 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Walter Kehowski, Sep 13 2005
EXTENSIONS
Duplicate terms removed and a(8)-a(26) from Donovan Johnson, Aug 30 2012
STATUS
approved