A120825 - OEIS

%I #14 May 09 2014 02:45:49

%S 1,5,15,51

%N Number of digits of primes with n consecutive digits ascending beginning with the digit seven.

%C Digits are in ascending order beginning with 7 and after 9 comes 0.

%C The sequence "Primes with n consecutive digits descending beginning with the digit seven" has only two terms below 6001, namely 1 and 5, which represent the primes 7 and 76543, respectively.

%e 1 is here because 7 is prime.

%e 5 is here because 78901 is prime.

%e 15 is here because 789012345678901 is a prime.

%e 51 is here because 789012345678901234567890123456789012345678901234567 is prime.

%t fQ[n_] := PrimeQ@ FromDigits@ Mod[6+Range@n, 10]; lst = {}; Do[ If[fQ@n, AppendTo[lst, n]; Print@n], {n, 5000}]; lst

%Y Cf. A006055, A120819, A120820, A120821, A120822, A120823, A120824, A120826, A120827.

%K base,hard,nonn

%O 1,2

%A _Robert G. Wilson v_, Jul 05 2006