login
A294679
Numbers k such that 9*10^k + 67 is prime.
0
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.
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] &]
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Nov 06 2017
STATUS
approved