%I #18 Aug 05 2015 11:52:45
%S 2,12,240,4032,16773120,4294901760,68719214592,1152921503533105152,
%T 1329227995784915871750885555673497600,
%U 95780971304118053647396688887409314154826126411694080,6582018229284824168619876730229320890292528855852623664389292032
%N Totient of the n-th perfect number.
%F a(n) = A000010(A000396(n)).
%t Map[EulerPhi, (# (# + 1))/2 & /@ Select[2^Range[100] - 1, PrimeQ]] (* _Michael De Vlieger_, Jul 25 2015, after _Harvey P. Dale_ at A000396 *)
%Y Cf. A000010, A000396, subsequence of A098203.
%K nonn
%O 1,1
%A _Carl Schildkraut_, Jul 12 2015
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