|
|
A103067
|
|
Numbers n such that 7*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
|
|
1
|
|
|
1, 4, 18, 28, 55, 1728, 1876, 1884, 6841, 10782, 25366, 98446, 137250
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
Also numbers n such that (71*10^n+1)/9 is prime.
|
|
LINKS
|
|
|
FORMULA
|
|
|
MATHEMATICA
|
Do[ If[ PrimeQ[(71*10^n + 1)/9], Print[n]], {n, 0, 10000}]
|
|
CROSSREFS
|
|
|
KEYWORD
|
more,nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|