OFFSET
1,1
COMMENTS
The more compact version A168159 gives many more terms, cf. formula. [M. F. Hasler, Nov 21 2009]
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..500 (terms 1..100 from Harvey P. Dale)
FORMULA
a(n) = 10^(n-1) + A168159(n). [M. F. Hasler, Nov 21 2009]
MATHEMATICA
f[n_] := Block[{k = 10^(n - 1)}, While[ !PrimeQ[k] || !PrimeQ[FromDigits@Reverse@IntegerDigits@k], k++ ]; k]; Array[f, 19] (* Robert G. Wilson v, Nov 19 2005 *)
lndp[n_]:=Module[{p=NextPrime[10^n]}, While[CompositeQ[IntegerReverse[ p]], p = NextPrime[ p]]; p]; Array[lndp, 20, 0] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 05 2019 *)
PROG
(PARI) for(x=1, 1e99, until( isprime(x=nextprime(x+1)) & isprime(eval(concat(vecextract(Vec(Str(x)), "-1..1")))), ); print1(x", "); x=10^#Str(x)-1) \\ M. F. Hasler, Nov 21 2009
(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) if c(p))
print([a(n) for n in range(1, 21)]) # Michael S. Branicky, Jun 27 2022
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Nov 12 2005
EXTENSIONS
More terms from Robert G. Wilson v, Nov 19 2005
STATUS
approved