OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..160
MAPLE
rev:= proc(n) local L, i;
L:= convert(n, base, 10);
add(L[-i]*10^(i-1), i=1..nops(L))
end proc;
R:= 3: X:= 3: XR:= 3:
for i from 2 to 50 do
for x from 1 by 2 do
d:= 1+ilog10(x);
t:= X*10^(1+ilog10(x)) + x;
if not isprime(t) then next fi;
xr:= rev(x);
tr:= XR+xr*10^(1+ilog10(XR));
if isprime(tr) then break fi;
od;
X:= t; XR:= tr; R:= R, x;
od:
R; # Robert Israel, Aug 09 2023
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Hans Havermann, Nov 08 2005
STATUS
approved