A240678 Primes p such that p*10+k is prime for exactly one value of the digit k.

11, 29, 41, 47, 71, 79, 83, 131, 137, 139, 151, 163, 173, 181, 191, 227, 257, 263, 277, 281, 293, 307, 311, 313, 359, 383, 449, 491, 503, 509, 557, 563, 569, 577, 587, 593, 601, 617, 647, 659, 661, 677, 683, 719, 739, 743, 751, 809, 821, 827, 857, 877, 881

Offset: 1

Author

Colin Barker, Apr 10 2014

Keywords

• nonn
• base

Examples

			11 is in the sequence because 113 is prime, but 111, 117 and 119 are not prime.
		

Links

• Colin Barker, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A067267, A119289, A240679, A240680, A240689.

Programs

Mathematica

Select[Prime[Range[200]],Total[Boole[PrimeQ[10 #+{1,3,7,9}]]]==1&] (* Harvey P. Dale, Apr 19 2019 *)

PARI

forprime(p=2, 1500, t=0; forstep(k=1, 9, 2, if(isprime(p*10+k), t++)); if(t==1, print1(p, ", ")))

Python

from sympy import isprime, primerange
def ok(p): return sum(1 for k in [1, 3, 7, 9] if isprime(p*10+k)) == 1
def aupto(limit): return [p for p in primerange(1, limit+1) if ok(p)]
print(aupto(881)) # Michael S. Branicky, Nov 29 2021