A064777 - OEIS

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A064777

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

1, 2, 3, 18, 42, 95, 524, 273585, 1735537, 4406057, 4406063, 4406188, 4406196, 4406341, 4406539, 4406541, 28703894, 73694240, 73694281, 73694287, 73694360, 73694363, 73694410, 3287860772, 3287860773, 3287860880, 3287860889, 3287860895, 3287860897

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..29.

EXAMPLE

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

MATHEMATICA

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

Select[Range[5000000], Divisible[Prime[#]-PrimePi[#], #]&] (* Harvey P. Dale, Aug 12 2013 *)

PROG

(PARI) isok(k) = ((prime(k) - primepi(k)) % k) == 0; \\ Michel Marcus, Jun 15 2021