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Least k such that prime(k) >= k*tau(k*n) where tau = A000005.
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%I #23 Apr 10 2020 14:44:59

%S 1,1,1,181,1,1061,1,1061,181,1061,1,40123,1,1061,1061,6473,1,40123,1,

%T 40123,1061,1061,1,1617211,181,1061,1061,40123,1,1617211,1,40123,1061,

%U 1061,1061,10553429,1,1061,1061,1617211,1,1617211,1,40123,40123,1061,1,69709687

%N Least k such that prime(k) >= k*tau(k*n) where tau = A000005.

%C Listed terms are = 1 or are primes.

%C a(n) = 1 iff n = 1 or n is prime. - _Bernard Schott_, Apr 10 2020

%o (PARI) a(n)=if(n<0,0,my(s=1); while(prime(s)<s*numdiv(s*n),s++); s)

%o (PARI) a(n)= my(k=1,p=2); while(p<k*numdiv(k*n), k++; p=nextprime(p+1)); k; \\ _Michel Marcus_, Apr 05 2020

%Y Cf. A000005.

%K nonn

%O 1,4

%A _Benoit Cloitre_, Sep 08 2002

%E More terms from _Jinyuan Wang_, Apr 05 2020

%E Name corrected by _Bernard Schott_, Apr 10 2020