OFFSET
1,1
COMMENTS
All terms == 2 (mod 3).
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(3)=17 is a term because 17 and 289171 are primes, where 17^2=289.
MAPLE
cat3:= proc(x) local t;
t:= 10*x+1;
x^2*10^(1+ilog10(t))+t
end proc:
select(t -> isprime(t) and isprime(cat3(t)), [2, seq(i, i=5..10000, 6)]);
MATHEMATICA
ppQ[n_]:=PrimeQ[FromDigits[IntegerDigits/@Join[n^2, n, 1]]]; Select[Prime[Range[500]], ppQ] (* Vincenzo Librandi, Jan 15 2019 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
J. M. Bergot and Robert Israel, Jan 14 2019
STATUS
approved