%I
%S 2,16,289,1681,10201,146689,1190281,10374841,103042801,1023424081,
%T 10009802401,100019755081,1000242014641,10001235475729,
%U 100001580006241,1000017101564209,10000044600049729,100000569832596889
%N First ndigit number m such that sigma(m) is prime.
%C Each term is of the form p^k where p is prime. For n > 1, k is even.
%C Can it be proved that a(n) exists for all n?
%K nonn,base
%O 1,1
%A _Farideh Firoozbakht_, Oct 10 2005
