OFFSET
1,2
COMMENTS
A139256 is a subsequence. - Michel Marcus, Dec 02 2013
LINKS
Ray Chandler, Table of n, a(n) for n = 1..1000 (using comment in formula section from David Wasserman and b-files for A007691 and A054030)
FORMULA
MATHEMATICA
kmax = 10^12;
okQ[n_] := AnyTrue[Most[Divisors[n]], DivisorSigma[1, #] == n&];
{1}~Join~Reap[Do[k = A007691[[i]]*A054030[[j]]; If[k <= kmax, Sow[k]], {i, Length[A007691]}, {j, Length[A054030]}]][[2, 1]] // Union // Select[#, okQ]& (* Jean-François Alcover, Oct 31 2019, after David Wasserman *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Apr 08 2003
EXTENSIONS
More terms from David Wasserman, Jun 28 2004
Description clarified by Ray Chandler, May 18 2017
STATUS
approved