|
| |
|
|
A281171
|
|
Numbers k such that (5*10^k + 37)/3 is prime.
|
|
1
|
|
|
|
1, 2, 5, 9, 13, 20, 21, 32, 33, 56, 73, 81, 149, 313, 455, 753, 1013, 1166, 1304, 1679, 15758, 15896, 21801, 41353, 45421, 131090, 151007
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,2
|
|
|
COMMENTS
|
For k > 1, numbers k such that the digit 1 followed by k-2 occurrences of the digit 6 followed by the digits 79 is prime (see Example section).
a(28) > 2*10^5.
|
|
|
LINKS
|
|
|
|
EXAMPLE
|
2 is in this sequence because (5*10^2 + 37) / 3 = 179 is prime.
Initial terms and associated primes:
a(1) = 1, 29;
a(2) = 2, 179;
a(3) = 5, 166679;
a(4) = 9, 1666666679;
a(5) = 13, 16666666666679; etc.
|
|
|
MATHEMATICA
|
Select[Range[0, 100000], PrimeQ[(5*10^# + 37) / 3] &]
|
|
|
CROSSREFS
|
|
|
|
KEYWORD
|
nonn,more,hard
|
|
|
AUTHOR
|
|
|
|
EXTENSIONS
|
|
|
|
STATUS
|
approved
|
| |
|
|
