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

Offset: 1

Author

Juri-Stepan Gerasimov, Jan 19 2009

Keywords

• nonn
• base
• less

Comments

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

Crossrefs

Cf. A000040, A109066, A141468.

Programs

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

Extensions

Corrected (17 and 479 inserted) by R. J. Mathar, May 05 2010