A292903 Numbers k such that (2*10^k + 547)/9 is prime.

0, 2, 3, 5, 15, 23, 24, 36, 45, 122, 168, 314, 390, 788, 818, 3588, 10502, 24467, 27356, 29955, 33074, 36669, 46776, 94604

Offset

1,2

Comments

For k>1, numbers such that k-2 occurrences of the digit 2 followed by the digits 83 is prime (see Example section).

a(25) > 2*10^5.

Links

Table of n, a(n) for n=1..24.

Makoto Kamada, Factorization of near-repdigit-related numbers.

Makoto Kamada, Search for 2w83

Example

3 is in this sequence because (2*10^3 + 547)/9 = 283 is prime.
Initial terms and primes associated:
a(1) = 0, 61;
a(2) = 2, 83;
a(3) = 3, 283;
a(4) = 5, 22283;
a(5) = 15, 222222222222283; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[(2*10^# + 547)/9] &]

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Sequence in context: A282616 A174418 A072246 * A296051 A248613 A024781

Adjacent sequences: A292900 A292901 A292902 * A292904 A292905 A292906

Keyword

nonn,more,hard

Author

Robert Price, Oct 09 2017

Status

approved