A280942 Numbers k such that (29*10^k - 77)/3 is prime.

1, 2, 12, 14, 31, 32, 42, 44, 69, 134, 146, 164, 560, 846, 1410, 1416, 1962, 1995, 2546, 3506, 4334, 7035, 12901, 20137, 42206, 45890, 58417, 106620, 126928, 197629

Offset

1,2

Comments

For k>1, numbers such that the digit 9 followed by k-2 occurrences of the digit 6 followed by the digits 41 is prime (see Example section).

a(31) > 2*10^5.

Links

Table of n, a(n) for n=1..30.

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

Makoto Kamada, Search for 96w41.

Example

2 is in this sequence because (29*10^2 - 77) / 3 = 941 is prime.
Initial terms and primes associated:
a(1) = 1, 71;
a(2) = 2, 941;
a(3) = 12, 9666666666641;
a(4) = 14, 966666666666641;
a(5) = 32, 96666666666666666666666666666641; etc.

Mathematica

Select[Range[1, 100000], PrimeQ[(29*10^# - 77) / 3] &]

Crossrefs

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

Sequence in context: A022368 A076484 A259128 * A270119 A340016 A260899

Adjacent sequences: A280939 A280940 A280941 * A280943 A280944 A280945

Keyword

nonn,more,hard

Author

Robert Price, Jan 11 2017

Extensions

a(28)-a(30) from Robert Price, Jan 31 2020

Status

approved