A066725 Primes whose product of digits + 1 is also prime.
2, 11, 23, 29, 41, 43, 47, 61, 67, 89, 149, 163, 167, 211, 223, 227, 229, 233, 251, 257, 263, 269, 281, 349, 367, 383, 419, 431, 433, 439, 463, 491, 521, 523, 569, 587, 613, 617, 631, 643, 659, 661, 673, 761, 769, 821, 827, 857, 883, 887, 929, 941, 967, 1123
Offset: 1
Examples
2 * 2 * 3 + 1 = 13, a prime; since 223 is also prime, it is a term of the sequence.
Links
- Harry J. Smith, Table of n, a(n) for n = 1..1000
Programs
-
Mathematica
Select[Prime[Range[200]],PrimeQ[Times@@IntegerDigits[#]+1]&] (* Harvey P. Dale, May 09 2012 *)
-
PARI
isok(p)={ isprime(p) && isprime(vecprod(digits(p)) + 1) } \\ Harry J. Smith, Mar 19 2010
Formula
Extensions
Terms a(35)-a(54) from Harry J. Smith, Mar 19 2010