A236670 Start with 6; thereafter, primes obtained by concatenating to the end of previous term the next smallest number that will produce a prime.

6, 61, 613, 6131, 613141, 61314119, 6131411917, 61314119171, 6131411917181, 613141191718127, 61314119171812789, 613141191718127893, 61314119171812789379, 6131411917181278937929, 61314119171812789379291, 61314119171812789379291111

Offset: 1

Author

Derek Orr, Jan 29 2014

Keywords

• nonn
• base

Comments

a(n+1) is the next smallest prime beginning with a(n). Initial term is 6. After a(1), these are the primes arising in A069608.

Examples

			a(1) = 6 by definition.
a(2) is the next smallest prime beginning with 6, so a(2) = 61.
a(3) is the next smallest prime beginning with 61, so a(3) = 613.
		

Crossrefs

Cf. A069608, A048553, A110773.

Programs

Python

import sympy
from sympy import isprime
def b(x):
  num = str(x)
  n = 1
  while n < 10**3:
    new_num = str(x) + str(n)
    if isprime(int(new_num)):
      print(int(new_num))
      x = new_num
      n = 1
    else:
      n += 1
b(6)