|
|
A282340
|
|
Numbers k such that (184*10^k - 1)/3 is prime.
|
|
0
|
|
|
0, 1, 2, 3, 21, 24, 25, 39, 42, 90, 192, 547, 3185, 3363, 4279, 4496, 4761, 5022, 6807, 13220, 13283, 13519, 25183, 37609, 84348, 87473, 112007, 211682
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,3
|
|
COMMENTS
|
Numbers k such that the digits 61 followed by k occurrences of the digit 3 is prime (see Example section).
a(29) > 3*10^5.
|
|
LINKS
|
|
|
EXAMPLE
|
2 is in this sequence because (184*10^2 - 1)/3 = 6133 is prime.
Initial terms and associated primes:
a(1) = 0, 61;
a(2) = 1, 613;
a(3) = 2, 6133;
a(4) = 3, 61333;
a(5) = 21, 61333333333333333333333; etc.
|
|
MATHEMATICA
|
Select[Range[0, 100000], PrimeQ[(184*10^# - 1)/3] &]
|
|
PROG
|
(PARI) isok(k) = isprime((184*10^k - 1)/3); \\ Michel Marcus, Feb 12 2017
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,more,hard
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|