|
|
A286431
|
|
Numbers k such that (22*10^k + 53)/3 is prime.
|
|
0
|
|
|
2, 3, 4, 5, 8, 9, 16, 17, 18, 36, 54, 69, 183, 200, 240, 846, 1424, 2511, 4750, 13854, 15414, 103450, 128094, 132746
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
For k>1, numbers such that the digit 7 followed by k-2 occurrences of the digit 3 followed by the digits 51 is prime (see Example section).
a(25) > 2*10^5.
|
|
LINKS
|
|
|
EXAMPLE
|
3 is in this sequence because (22*10^3 + 53)/3 = 7351 is prime.
Initial terms and primes associated:
a(1) = 2, 751;
a(2) = 3, 7351;
a(3) = 4, 73351;
a(4) = 5, 733351;
a(5) = 8, 733333351; etc.
|
|
MATHEMATICA
|
Select[Range[0, 100000], PrimeQ[(22*10^# + 53)/3] &]
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,more,hard
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|