OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..722
EXAMPLE
3+10^1=13, 13 and 31 are symmetric primes with symmetric digits;
7+10^2=107, 107 and 701 are symmetric primes with symmetric digits;
9+10^3=1009, 1009 and 9001 are symmetric primes with symmetric digits.
MAPLE
revdigs:= proc(n) local L, i;
L:= convert(n, base, 10);
add(L[-i]*10^(i-1), i=1..nops(L))
end proc:
f:= proc(n) local k, m;
for k from 3 by 2 do
m:= k+10^n;
if isprime(m) and isprime(revdigs(m)) then return k fi
od
end proc:
map(f, [$1..100]); # Robert Israel, Nov 09 2017
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Pierre CAMI, Sep 16 2006
EXTENSIONS
Definition clarified, a(28) corrected, and more terms added by Robert Israel, Nov 09 2017
STATUS
approved