|
|
A290964
|
|
Numbers k such that (35*10^k - 593)/9 is prime.
|
|
1
|
|
|
3, 5, 6, 14, 24, 84, 87, 207, 734, 797, 1743, 2211, 3539, 5871, 5949, 6954, 8309, 10896, 12771, 22382, 35112, 38267, 69866, 121229, 125754, 133979
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
For k>1, numbers such that the digit 3 followed by k-2 occurrences of the digit 8 followed by the digits 23 is prime (see Example section).
a(27) > 2*10^5.
|
|
LINKS
|
|
|
EXAMPLE
|
5 is in this sequence because (35*10^5 - 593)/9 = 388823 is prime.
Initial terms and primes associated:
a(1) = 3, 3823;
a(2) = 5, 388823;
a(3) = 6, 3888823;
a(4) = 14; 388888888888823;
a(5) = 24, 3888888888888888888888823; etc.
|
|
MATHEMATICA
|
Select[Range[2, 100000], PrimeQ[(35*10^# - 593)/9] &]
|
|
PROG
|
(PARI) isok(n) = ispseudoprime((35*10^n - 593)/9) \\ Altug Alkan, Aug 15 2017
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,more,hard
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|