A092993 - OEIS

%I #12 Oct 20 2014 08:19:28

%S 23,0,53,73,113,13131313133,173,193,233,293,313,373,41413,433,

%T 47474747474747474747474747473,53535353535353535353535353533,593,613,

%U 673,71713,733,0,83833,89898989893,97973,1013,1033,1071071071073,1093

%N Smallest prime of the form concatenation(s) of prime(n) with itself followed by a 3, or 0 if no such prime exists.

%C Start with p=prime(n). If concat(p,3) is prime, then this is a(n), else consider concat(p,p,3), and so on.

%e For a(1), start with prime(1)=2. Since appending a digit 3 yields the prime 23, a(1)=23.

%e For a(2), start with prime(2)=3. Since concatenating any number of digits '3' never yields a prime, a(2)=0.

%e For a(6), starting with prime(6)=13, one has to take 5 concatenations of itself before a prime is obtained when a final digit '3' is appended, thus a(6)=13131313133.

%e a(22)=0 since the concatenation of prime(22)=79 with itself, followed by a 3, is always composite. - _Giovanni Resta_, Apr 07 2006

%Y Cf. A092992, A092994, A092995.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Mar 28 2004

%E a(15)-a(21) from _Stefan Steinerberger_, Nov 09 2005

%E More terms from _Giovanni Resta_, Apr 07 2006