OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..6933
EXAMPLE
a(3)=51 is a member because 51=3*17 and both 317 and 173 are primes.
MAPLE
N:= 20000: # for all terms <= N
catt:= proc(n, m) 10^(1+ilog10(m))*n+m end proc:
Primes:= select(isprime, [seq(i, i=3..N/3)]):
SP:= [seq(seq([p, q], q = select(`<=`, Primes, min(p, N/p))), p=Primes)]:
B:=select(t -> isprime(catt(t[1], t[2])) and isprime(catt(t[2], t[1])), SP):
sort(map(convert, B, `*`));
CROSSREFS
KEYWORD
nonn,base
AUTHOR
J. M. Bergot and Robert Israel, Dec 14 2019
STATUS
approved