A155048 - OEIS

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A155048

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

7, 11, 17, 19, 23, 191, 199, 211, 227, 251, 277, 281, 311, 337, 347, 353, 359, 373, 383, 389, 397, 401, 409, 419, 439, 463, 467, 479, 523, 547, 557, 569, 571, 577, 593, 599, 613, 619, 641, 643, 653, 659, 673, 677, 683, 701, 709, 743, 751, 757, 769, 787, 809

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

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

LINKS

Table of n, a(n) for n=1..53.

PROG

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

isok(p) = my(nbp=f(prime(p))); isprime(p) && (2*f(p) == #digits(prime(p))); \\ Michel Marcus, Feb 18 2021

CROSSREFS

Cf. A000040, A109066, A141468.