OFFSET
1,1
COMMENTS
All terms == 1 (mod 6).
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(3)=967 is a term because 967 is prime and 9042310639350899671 is prime, where 967^3=904231063 and 967^2=935089.
MAPLE
cat4:= proc(x) local t;
t:= 10*x+1;
t:= x^2*10^(1+ilog10(t))+t;
x^3*10^(1+ilog10(t))+t;
end proc:
select(t -> isprime(t) and isprime(cat4(t)), [seq(i, i=1..10^5, 6)]);
MATHEMATICA
pppQ[n_]:=PrimeQ[FromDigits[IntegerDigits/@Join[n^3, n^2, n, 1]]]; Select[Prime[Range[4500]], pppQ] (* Vincenzo Librandi, Jan 15 2019 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
J. M. Bergot and Robert Israel, Jan 14 2019
STATUS
approved