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 A085720 #15 Aug 15 2021 18:54:47
%S A085720 7,37,157,185,187,271,301,355,475,485,523,533,577,611,653,661,667,731,
%T A085720 733,755,761,791,853,911,913,937,983,1085,1111,1187,1205,1253,1397,
%U A085720 1417,1585,1631,1655,1685,1697,1711,1723,1841,1907,1975,2035,2077,2105,2185
%N A085720 Start of a run of 7 successive numbers which when concatenated form a prime.
%C A085720 Concatenation of three and six successive numbers are always composite.
%C A085720 Primes as concatenation of two, four and five successive numbers are in A030458, A030471, A052087, A052088, A052089.
%H A085720 Harvey P. Dale, <a href="/A085720/b085720.txt">Table of n, a(n) for n = 1..1000</a>
%t A085720 f[n_] := FromDigits[ Flatten[ Table[ IntegerDigits[i], {i, n, n + 6}]]]; Select[ Range[2190], PrimeQ[ f[ # ]] & ]
%t A085720 Select[Range[2500],PrimeQ[FromDigits[Flatten[IntegerDigits/@Range[#,#+6]]]]&] (* _Harvey P. Dale_, Aug 15 2021 *)
%Y A085720 Cf. A030458, A030471, A052087, A052088, A052089.
%K A085720 easy,nonn,base
%O A085720 1,1
%A A085720 _Zak Seidov_, Jun 27 2003
%E A085720 Edited by _Robert G. Wilson v_, Jun 28 2003
%E A085720 Edited by _Charles R Greathouse IV_, Apr 24 2010