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Indices of perfect numbers (A000396) in the sequence of multiply-perfect numbers (A007691).
5

%I #8 Dec 15 2016 15:23:53

%S 2,3,5,7,13,19,25,41,110,192,229,294

%N Indices of perfect numbers (A000396) in the sequence of multiply-perfect numbers (A007691).

%C The sequence contains no further entries between 294 and 1600. - _R. J. Mathar_, May 26 2011

%e a(7) is 25 because the 25th multiply-perfect number A007691(25)=137438691328 is also the 7th perfect number A000396(7).

%Y Cf. A000396, A007691.

%K more,nonn

%O 1,1

%A _Omar E. Pol_, Jan 13 2009