|
|
A285379
|
|
Numbers k such that (47*10^k + 133)/9 is prime.
|
|
0
|
|
|
1, 3, 4, 6, 7, 9, 16, 45, 73, 75, 94, 217, 241, 294, 1074, 2133, 2379, 3504, 8241, 16218, 16387, 18135, 31771, 47331, 58456, 72696, 76672
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
For k > 1, numbers k such that the digit 5 followed by k-2 occurrences of the digit 2 followed by the digits 37 is prime (see Example section).
a(28) > 2*10^5.
|
|
LINKS
|
|
|
EXAMPLE
|
4 is in this sequence because (47*10^4 + 133)/9 = 52237 is prime.
Initial terms and associated primes:
a(1) = 1, 67;
a(2) = 3, 5237;
a(3) = 4, 52237;
a(4) = 6, 5222237;
a(5) = 7, 52222237; etc.
|
|
MATHEMATICA
|
Select[Range[0, 100000], PrimeQ[(47*10^# + 133)/9] &]
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,more,hard
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|