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Numbers n such that pi(n) = prime(d_1)*prime(d_2)*...*prime(d_k) where d_1 d_2 ... d_k is the decimal expansion of n.
4

%I #24 Mar 06 2019 12:02:54

%S 123,5224,11166,51174,172451,546322,14355351,23539612,23539621,

%T 24322837,122924349,4575242147,42256772524,283186883151,623286236455,

%U 665318971119,665318971191,5257788212426,27452719198281,273643846355134,787812731751347,787812731751374

%N Numbers n such that pi(n) = prime(d_1)*prime(d_2)*...*prime(d_k) where d_1 d_2 ... d_k is the decimal expansion of n.

%C a(n) must necessarily be a zeroless number, i.e., the sequence is a subsequence of A052382. - _Chai Wah Wu_, Mar 04 2019

%e 122924349 is in the sequence because pi(122924349) = P(1)*P(2)*P(2)*P(9)*P(2)*P(4)*P(3)*P(4)*P(9) where P(i) is i-th prime.

%t Do[d=IntegerDigits[n];k=Length[d];If[ !MemberQ[d, 0]&&PrimePi[n]==Product[Prime[d[[j]]], {j, k}], Print[n]], {n, 230000000}]

%Y Cf. A052382, A097227, A098684, A098685, A160040.

%K base,nonn

%O 1,1

%A _Farideh Firoozbakht_, Sep 24 2004

%E Entries corrected by _Robert G. Wilson v_, May 04 2009

%E a(13)-a(17) from _Donovan Johnson_, Jul 12 2010

%E a(18) from _Giovanni Resta_, Apr 01 2017

%E a(19) from _Chai Wah Wu_, Mar 05 2019

%E a(20)-a(22) from _Chai Wah Wu_, Mar 06 2019