|
|
A282277
|
|
Numbers k such that (23*10^k + 97)/3 is prime.
|
|
0
|
|
|
3, 6, 11, 14, 20, 38, 55, 206, 1327, 1676, 1715, 1814, 2030, 2406, 2599, 3251, 4493, 5066, 6029, 8745, 24918, 26672, 70363, 77556
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
For k > 1, numbers k such that the digit 7 followed by k-2 occurrences of the digit 6 followed by the digits 99 is prime (see Example section).
a(25) > 2*10^5.
|
|
LINKS
|
|
|
EXAMPLE
|
6 is in this sequence because (23*10^6 + 97)/3 = 7666699 is prime.
Initial terms and associated primes:
a(1) = 3, 7699;
a(2) = 6, 7666699;
a(3) = 11, 766666666699;
a(4) = 14, 766666666666699;
a(5) = 20, 766666666666666666699; etc.
|
|
MATHEMATICA
|
Select[Range[0, 100000], PrimeQ[(23*10^# + 97)/3] &]
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,more,hard
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|