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 A089786 #5 Nov 17 2014 16:34:24
%S A089786 73,197,7129,10141,15161,19379,271109,373157,593251,757331,983431,
%T A089786 997433,1069463,1231547,1361599,1531661,1571683,1627727,1831811,
%U A089786 2069911,2161967,2213977,24731093,25311103,26931193,27131213,27911237,28191259
%N A089786 Primes of the form prime(2k) followed by prime(k).
%H A089786 Harvey P. Dale, <a href="/A089786/b089786.txt">Table of n, a(n) for n = 1..1000</a>
%e A089786 10141 is a term as a concatenation of prime(26)=101 followed by prime(13)=41.
%p A089786 a:=proc(k) local s,m: s:= [op(convert(ithprime(k),base,10)),op(convert(ithprime(2*k),base,10))]: m:=add(s[j]*10^(j-1),j=1..nops(s)): if not isprime(m) then RETURN(NULL) else RETURN(m) fi: end; seq(a(k),k=1..250); (C. Ronaldo)
%t A089786 Select[Table[FromDigits[Flatten[IntegerDigits/@{Prime[2n],Prime[n]}]],{n,250}],PrimeQ] (* _Harvey P. Dale_, Nov 17 2014 *)
%Y A089786 Cf. A089782, A089783, A089784, A089785, A089787.
%K A089786 base,nonn
%O A089786 1,1
%A A089786 _Amarnath Murthy_, Nov 24 2003
%E A089786 Corrected and extended by C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 25 2004