|
|
A294915
|
|
Numbers k such that (13*10^k - 139)/9 is prime.
|
|
0
|
|
|
3, 7, 46, 51, 87, 124, 141, 301, 309, 400, 667, 1749, 2512, 3859, 4323, 4515, 9238, 9592
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
For k > 1, numbers such that the digit 1 followed by k-2 occurrences of the digit 4 followed by the digits 29 is prime (see Example section).
a(18) > 2*10^5.
|
|
LINKS
|
|
|
EXAMPLE
|
3 is in this sequence because (13*10^3 - 139)/9 = 1429 is prime.
Initial terms and primes associated:
a(1) = 3, 1429;
a(2) = 7, 14444429;
a(3) = 46, 14444444444444444444444444444444444444444444429;
a(4) = 51, 1444444444444444444444444444444444444444444444444429; etc.
|
|
MATHEMATICA
|
Select[Range[2, 100000], PrimeQ[(13*10^# - 139)/9] &]
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,more,hard
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|