OFFSET

1,1

COMMENTS

a(n+1) is the next smallest prime beginning with a(n). Initial term is 4.

After a(1), these are the primes arising in A069606.

EXAMPLE

a(1) = 4 by definition.

a(2) is the next smallest prime beginning with 4, so a(2) = 41.

a(3) is the next smallest prime beginning with 41, so a(3) = 419.

...and so on.

MATHEMATICA

NestList[Module[{k=1}, While[!PrimeQ[#*10^IntegerLength[k]+k], k+=2]; #*10^IntegerLength[k]+ k]&, 4, 20] (* Harvey P. Dale, Jul 20 2024 *)

PROG

(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(4)

CROSSREFS

KEYWORD

nonn,base

AUTHOR

Derek Orr, Jan 27 2014

STATUS

approved