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%I #15 Dec 15 2017 17:34:49
%S 1,2,56,80,85,2527,2569,2723,2807,7864,7976,22941,113488,174449,
%T 461403,1302379,8513821,14348051,70110091,70111621,70112369,249046528
%N Numbers n such that us(n) = number of primes <= n, where usigma(n) = sum of unitary divisors of n (A034448), us(n) is usigma(n)-n.
%o (PARI) us(n) = sumdiv(n,d, if(gcd(d,n/d)==1,d)); f(n)=s=0; for(x=1,n, if(isprime(x),s++)); s; for(n=1,10^6, if(us(n)-n==f(n),print(n)))
%K nonn
%O 1,2
%A _Naohiro Nomoto_
%E a(12) from _Jason Earls_, Sep 06 2001
%E a(13) - a(15) from _Nathaniel Johnston_, Apr 29 2011
%E a(16)-a(22) from _Donovan Johnson_, Jul 24 2012
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