OFFSET
1,1
LINKS
Jens Kruse Andersen, Table of n, a(n) for n = 1..10000
EXAMPLE
39 is included because 1393939 is a prime.
MATHEMATICA
cQ[n_, i_]:=Module[{idn=IntegerDigits[n]}, PrimeQ[FromDigits[Flatten[ Join[ {1}, Table[idn, {i}]]]]]]; Select[Range[1000], cQ[#, 3]&]
c13nQ[n_]:=PrimeQ[FromDigits[PadRight[{1}, 3 IntegerLength[n]+1, RotateRight[ IntegerDigits[n]]]]]; Select[Range[700], c13nQ] (* Harvey P. Dale, Aug 14 2017 *)
PROG
(Python)
from sympy import isprime
for n in range(10**3):
..if isprime(int('1'+3*str(n))):
....print(n, end=', ')
# Derek Orr, Aug 17 2014
(PARI) s=[]; for(n=1, 10^3, d=length(Str(n)); if(isprime(10^(3*d)+(10^(3*d)-1)/(10^d-1)*n), s=concat(s, n))); s \\ Jens Kruse Andersen, Aug 18 2014
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Harvey P. Dale, Aug 17 2014
STATUS
approved