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%I #13 Jul 05 2016 03:47:50
%S 1,2,9,85,2569,2723,2807,174449,1302379,8513821,10518107,14348051,
%T 70110091,70111621,70112369,10910880311,43908943297,4224496855063
%N Numbers n such that sigma(n) - n = {number of primes <= n}.
%o (PARI) isok(n) = (sigma(n)-n == primepi(n)) \\ _Michel Marcus_, Jul 14 2013
%K nonn,more
%O 1,2
%A _Naohiro Nomoto_
%E More terms from Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), Apr 09 2002
%E a(16)-a(17) from _Donovan Johnson_, Sep 03 2008
%E a(18) from _Giovanni Resta_, Jul 05 2016
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