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 A120825 #30 Apr 07 2025 22:57:05
%S A120825 1,5,15,51,8411
%N A120825 a(n) consecutive digits ascending beginning with the digit 7 give a prime.
%C A120825 Digits are in ascending order beginning with 7 and after 9 comes 0.
%C A120825 The sequence "a(n) consecutive digits descending beginning with the digit 7 give a prime" has only two terms below 6001, namely 1 and 5, which represent the primes 7 and 76543, respectively.
%C A120825 a(6) >= 100000. - _Michael S. Branicky_, Apr 07 2025
%e A120825 1 is here because 7 is prime.
%e A120825 5 is here because 78901 is prime.
%e A120825 15 is here because 789012345678901 is a prime.
%e A120825 51 is here because 789012345678901234567890123456789012345678901234567 is prime.
%t A120825 fQ[n_] := PrimeQ@ FromDigits@ Mod[6+Range@n, 10]; lst = {}; Do[ If[fQ@n, AppendTo[lst, n]; Print@n], {n, 5000}]; lst
%Y A120825 Cf. A006055, A120819, A120820, A120821, A120822, A120823, A120824, A120826, A120827.
%K A120825 nonn,base,hard,more
%O A120825 1,2
%A A120825 _Robert G. Wilson v_, Jul 05 2006
%E A120825 a(5) from _Bert Dobbelaere_, Apr 01 2025