A064777 - OEIS

%I #23 Jun 15 2021 08:06:01

%S 1,2,3,18,42,95,524,273585,1735537,4406057,4406063,4406188,4406196,

%T 4406341,4406539,4406541,28703894,73694240,73694281,73694287,73694360,

%U 73694363,73694410,3287860772,3287860773,3287860880,3287860889,3287860895,3287860897

%N Numbers k such that prime(k) - pi(k) is divisible by k.

%e k = 18 is a term: prime(18) = 61, pi(18) = 7, and (61-7)/18 = 54/18 = 3.

%t Do[ If[ IntegerQ[ (Prime[n] - PrimePi[n])/n ], Print[n]], {n, 1, 6*10^7} ]

%t Select[Range[5000000],Divisible[Prime[#]-PrimePi[#],#]&] (* _Harvey P. Dale_, Aug 12 2013 *)

%o (PARI) isok(k) = ((prime(k) - primepi(k)) % k) == 0; \\ _Michel Marcus_, Jun 15 2021

%Y Cf. A000040, A000720, A065139, A111181.

%K nonn

%O 1,2

%A _Labos Elemer_ and _Robert G. Wilson v_, Oct 18 2001

%E a(18)-a(23) from _Donovan Johnson_, Apr 23 2010

%E a(24)-a(29) from _Donovan Johnson_, Oct 17 2012