Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #8 Sep 27 2023 12:05:00
%S 23,37,523,719,1117,1319,1723,1931,2341,2953,3137,3761,4153,4373,4759,
%T 53101,59107,6173,6779,71167,73127,79103,8389,89101,97103,101107,
%U 103307,107137,109139,113131,127139,131149,137191,139199,149173,151157,157163
%N Smallest prime obtained as a concatenation of prime(n) and prime(m) with m > n.
%H Harvey P. Dale, <a href="/A113893/b113893.txt">Table of n, a(n) for n = 1..1000</a>
%e a(6) = 1319 as 1317 is composite. prime(6) = 13.
%t spc[n_]:=Module[{p1=Prime[n],p2},p2=NextPrime[p1];While[!PrimeQ[ p1* 10^IntegerLength[ p2]+p2],p2 = NextPrime[p2]];p1*10^IntegerLength[ p2]+p2]; Array[spc,40] (* _Harvey P. Dale_, Apr 05 2018 *)
%K base,nonn
%O 1,1
%A _Amarnath Murthy_, Nov 18 2005
%E More terms from _Stefan Steinerberger_ and _Jim Nastos_, Nov 18 2005