OFFSET
1,1
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..527
MATHEMATICA
f[n_] := Block[{k = 10^n}, While[ !PrimeQ[k] || !PrimeQ[FromDigits@Reverse@IntegerDigits@k], k-- ]; k]; Array[f, 19] (* Robert G. Wilson v, Nov 19 2005 *)
Table[Module[{p=NextPrime[10^e, -1]}, While[CompositeQ[IntegerReverse[p]], p=NextPrime[p, -1]]; p], {e, 20}] (* Harvey P. Dale, Mar 01 2025 *)
PROG
(Python)
from sympy import isprime
def c(n): return isprime(n) and isprime(int(str(n)[::-1]))
def a(n): return next(p for p in range(10**n-1, 10**(n-1), -2) if c(p))
print([a(n) for n in range(1, 21)]) # Michael S. Branicky, Jun 27 2022
CROSSREFS
KEYWORD
base,nonn,changed
AUTHOR
Amarnath Murthy, Nov 12 2005
EXTENSIONS
More terms from Robert G. Wilson v, Nov 19 2005
a(19) and beyond from Michael S. Branicky, Jun 27 2022
STATUS
approved