A120825 Number of digits of primes with n consecutive digits ascending beginning with the digit seven.

1, 5, 15, 51

Offset

1,2

Comments

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

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.

Links

Table of n, a(n) for n=1..4.

Example

1 is here because 7 is prime.
5 is here because 78901 is prime.
15 is here because 789012345678901 is a prime.
51 is here because 789012345678901234567890123456789012345678901234567 is prime.

Mathematica

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

Crossrefs

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

Sequence in context: A029609 A014274 A363510 * A199985 A255442 A149576

Adjacent sequences: A120822 A120823 A120824 * A120826 A120827 A120828

Keyword

base,hard,nonn

Author

Robert G. Wilson v, Jul 05 2006

Status

approved