A294679 Numbers k such that 9*10^k + 67 is prime.

1, 2, 3, 4, 6, 8, 16, 24, 32, 103, 1436, 6144, 6472, 6951, 8920, 9598, 12028, 13803, 21867, 23893, 46140

Offset

1,2

Comments

For k>1, numbers k such that the digit 9 followed by k-2 occurrences of the digit 0 followed by the digits 67 is prime (see Example section).

a(22) > 2*10^5.

Links

Table of n, a(n) for n=1..21.

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

Makoto Kamada, Search for 90w67.

Example

2 is in this sequence because 9*10^2 + 67 = 967 is prime.
Initial terms and associated primes:
a(1) = 1, 157;
a(2) = 2, 967;
a(3) = 3, 9067;
a(4) = 4, 90067;
a(5) = 6, 90067; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[9*10^# + 67] &]

Crossrefs

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

Sequence in context: A298072 A111023 A261751 * A333160 A345250 A008324

Adjacent sequences: A294676 A294677 A294678 * A294680 A294681 A294682

Keyword

nonn,more,hard

Author

Robert Price, Nov 06 2017

Status

approved