A294127 Numbers k such that (44*10^k - 503)/9 is prime.

2, 5, 8, 10, 11, 35, 74, 107, 170, 196, 281, 748, 1124, 2597, 5189, 5650, 8453, 10822, 24554, 54596, 85370, 140410, 188999

Offset

1,1

Comments

For k>1, numbers such that the digit 4 followed by k-2 occurrences of the digit 8 followed by the digits 33 is prime (see Example section).

a(24) > 2*10^5.

Links

Table of n, a(n) for n=1..23.

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

Makoto Kamada, Search for 48w33

Example

2 is in this sequence because (44*10^2 - 503)/9 = 433 is prime.
Initial terms and primes associated:
a(1) = 2, 433;
a(2) = 5, 488833;
a(3) = 8, 488888833;
a(4) = 10, 48888888833;
a(5) = 11, 488888888833; etc.

Mathematica

Select[Range[2, 100000], PrimeQ[(44*10^# - 503)/9] &]

Crossrefs

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

Sequence in context: A338388 A237525 A290578 * A166955 A286808 A121294

Adjacent sequences: A294124 A294125 A294126 * A294128 A294129 A294130

Keyword

nonn,more,hard

Author

Robert Price, Oct 23 2017

Extensions

a(22)-a(23) from Robert Price, Dec 23 2018

Status

approved