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 A102478 #10 Jun 27 2015 12:45:51 %S A102478 21,39,51,54,90,96,135,150,156,165,171,195,210,261,270,306,330,411, %T A102478 420,441,501,570,615,636,741,771,816,885,1050,1095,1341,1371,1536, %U A102478 1599,1704,1821,1914,2121,2226,2286,2370,2394,2499,2811,2859,2916,3051,3129,3714 %N A102478 Numbers n such that the concatenations (2*n),(2*n-1) and (2*n),(2*n+1) give twin primes. %H A102478 Harvey P. Dale, <a href="/A102478/b102478.txt">Table of n, a(n) for n = 1..8000</a> %F A102478 a(n) = A068700(n) / 2. - _Reinhard Zumkeller_, Jun 27 2015 %e A102478 2*21=42, 4241 and 4243 are twin primes so a(1)=21 %e A102478 2*39=78, 7877 and 7879 are twin primes so a(2)=39 %t A102478 concatQ[n_]:=Module[{idn=IntegerDigits[2n],concatidn},concatidn=FromDigits[Join[idn,idn]];And@@PrimeQ[{concatidn-1,concatidn+1}]]; Select[Range[4000],concatQ] (* _Harvey P. Dale_, Feb 07 2012 *) %o A102478 (Haskell) %o A102478 a102478 = flip div 2 . a068700 -- _Reinhard Zumkeller_, Jun 27 2015 %Y A102478 Cf. A068700. %K A102478 nonn,base %O A102478 1,1 %A A102478 _Pierre CAMI_, Feb 24 2005 %E A102478 Edited by _Charles R Greathouse IV_, Apr 29 2010