A155048 - OEIS

%I #16 Feb 19 2021 02:54:48

%S 7,11,17,19,23,191,199,211,227,251,277,281,311,337,347,353,359,373,

%T 383,389,397,401,409,419,439,463,467,479,523,547,557,569,571,577,593,

%U 599,613,619,641,643,653,659,673,677,683,701,709,743,751,757,769,787,809

%N Primes p such that number of prime digits of prime(p) = number of nonprime digits of prime(p).

%C Prime digits are 2, 3, 5 or 7, nonprime digit are 0, 1, 4, 6, 8 or 9.

%o (PARI) f(n) = #select(isprime, digits(prime(n))); \\ A109066

%o isok(p) = my(nbp=f(prime(p))); isprime(p) && (2*f(p) == #digits(prime(p)));  \\ _Michel Marcus_, Feb 18 2021

%Y Cf. A000040, A109066, A141468.

%K nonn,base,less

%O 1,1

%A _Juri-Stepan Gerasimov_, Jan 19 2009

%E Corrected (17 and 479 inserted) by _R. J. Mathar_, May 05 2010