|
|
A147556
|
|
Largest prime factor of prime(n)-th repunit number.
|
|
4
|
|
|
11, 37, 271, 4649, 513239, 265371653, 5363222357, 1111111111111111111, 11111111111111111111111, 77843839397, 57336415063790604359, 2212394296770203368013, 201763709900322803748657942361
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
The sequence of repunit primes is a subsequence of this sequence.
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
Prime(15)=47 and (10^47-1)/9 = 35121409*316362908763458525001406154038726382279, so a(15)=316362908763458525001406154038726382279.
|
|
MATHEMATICA
|
Table[FactorInteger[FromDigits[PadRight[{}, n, 1]]][[-1, 1]], {n, Prime[ Range[15]]}] (* Harvey P. Dale, Feb 23 2016 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|