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%I #19 Sep 10 2016 16:29:15
%S 1,2,4,13,16,17,28,34,90,100,132,331,534,7923
%N Numbers n such that b(n) is a prime, where b(1) = prime(1) = 2, b(n) = 10*b(n-1) + (prime(n) mod 10).
%C Primes in the sequence b(n) are 2, 23, 2357, 2357137939171, ...
%p Res:= NULL: p:= 0: b:= 0:
%p for n from 1 to 600 do
%p p:= nextprime(p);
%p b:= 10*b + (p mod 10);
%p if isprime(b) then Res:= Res, n fi
%p od:
%p Res; # _Robert Israel_, Sep 05 2016
%t b[1] = Prime@ 1; b[n_] := b[n] = 10 b[n - 1] + Mod[Prime@ n, 10]; Select[Range[10^3], PrimeQ@ b[#] &] (* _Michael De Vlieger_, Sep 06 2016 *)
%o (PARI) b(n) = if (n==1, 2, 10*b(n-1) + (prime(n) % 10));
%o isok(n) = isprime(b(n)); \\ _Michel Marcus_, Sep 05 2016
%o (PARI) list(lim)=my(v=List(),s,n); forprime(p=2,, if(n++>lim, return(Vec(v))); if(ispseudoprime(s=10*s+p%10), listput(v, n))) \\ _Charles R Greathouse IV_, Sep 05 2016
%Y Cf. A007652, A069151.
%K nonn,base
%O 1,2
%A _Thomas Ordowski_, Sep 05 2016
%E a(7)-a(13) from _Michel Marcus_, Sep 05 2016
%E a(14) from _Robert Israel_, Sep 05 2016
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