This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A225216 #9 May 03 2013 02:19:48
%S A225216 0,1,0,1,2,1,2,2,4,2,2,2,4,1,4,5,4,3,4,5,6,4,5,5,6,5,6,5,3,8,4,6,8,7,
%T A225216 8,7,5,6,8,8,4,9,7,5,10,5,9,5,8,8,10,8,8,14,10,7,14,8,8,11,10,13,8,10,
%U A225216 10,10,11,12,13,8,11,14,12,11,13,13,13,16
%N A225216 Let p = n-th prime. Then a(n) = number of primes generated by prepending to the digits of p the digits of q, where q is any prime less than p.
%C A225216 The graph makes it apparent that there are fewer primes generated when the prime p increases its length from 3 to 4 and 4 to 5 digits. - _T. D. Noe_, May 03 2013
%H A225216 T. D. Noe, <a href="/A225216/b225216.txt">Table of n, a(n) for n = 1..10000</a>
%e A225216 a(2)=1 since second prime 3 generates 23. Also a(7)=2 since for the seventh prime 17 we have two primes 317 and 1117.
%t A225216 con[x_,y_] := FromDigits[Join[IntegerDigits[Prime[x]], IntegerDigits[Prime[y]]]]; t={}; Do[c=0; Do[If[PrimeQ[con[i,n]], c=c+1], {i,n}]; AppendTo[t,c], {n,78}]; t
%Y A225216 Cf. A224748, A224908.
%K A225216 nonn,base
%O A225216 1,5
%A A225216 _Jayanta Basu_, May 02 2013