|
|
A293825
|
|
Numbers k such that (29*10^k + 673)/9 is prime.
|
|
0
|
|
|
1, 2, 4, 7, 14, 19, 20, 22, 29, 40, 64, 169, 173, 1513, 2357, 3193, 4198, 11864, 18182, 19576, 31175, 38030, 57967, 122996
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
For k>1, numbers such that the digit 3 followed by k-2 occurrences of the digit 2 followed by the digits 97 is prime (see Example section).
a(25) > 2*10^5.
|
|
LINKS
|
|
|
EXAMPLE
|
2 is in this sequence because (29*10^2 + 673)/9 = 397 is prime.
Initial terms and primes associated:
a(1) = 1, 107;
a(2) = 2, 397;
a(3) = 4, 32297;
a(4) = 7, 32222297;
a(5) = 14, 322222222222297; etc.
|
|
MATHEMATICA
|
Select[Range[0, 100000], PrimeQ[(29*10^# + 673)/9] &]
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,more,hard
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|