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 A104645 #11 Aug 22 2019 10:01:35
%S A104645 10,6,20,24,24,60,18,48,100,48,156,74,88,68,42,126,366,106,186,136,
%T A104645 228,104,30,246,52,218,814,58,536,174,90,924,180,298,120,330,96,508,
%U A104645 504,60,762,588,330,138,552,726,452,634,660,354,534,1770,52,262,834,790,250,624
%N A104645 Difference between the previous and the next primes to x, where x is the number obtained from concatenation of the first n primes (A019518).
%F A104645 a(n) = A151800(A019518(n)) - A151799(A019518(n)).
%e A104645 For n=4, concatenate(2,3,5,7) gives 2357. The closest other primes are 2371 and 2351 and their difference is a(4)=20.
%t A104645 <<NumberTheory`NumberTheoryFunctions` sz[x_] :=FromDigits[Flatten[Table[IntegerDigits[Prime[j]], {j, 1, x}], 1]] Table[NextPrime[sz[w]]-PreviousPrime[sz[w]], {w, 1, 100}]
%o A104645 (PARI) A019518(n)=my(k="");forprime(p=2,prime(n),k=Str(k,p));eval(k)
%o A104645 a(n)=my(k=A019518(n));nextprime(k+1)-precprime(k-1) \\ _Charles R Greathouse IV_, Apr 28 2010
%Y A104645 Cf. A019518, A074809, A104462, A104463.
%K A104645 nonn,base
%O A104645 2,1
%A A104645 _Labos Elemer_, Mar 18 2005
%E A104645 Corrected, extended, and edited by _Charles R Greathouse IV_, Apr 28 2010