|
|
A352736
|
|
a(n) is the smallest b >= 2 such that 1 + Sum_{k=0..n} b^(2^k) is prime, or 1 if no such b exists.
|
|
0
|
|
|
2, 2, 2, 1, 6, 3, 448, 107, 104, 1, 4556, 1, 24124, 121209, 368, 177817, 48330, 1
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,1
|
|
COMMENTS
|
Polynomial factorizations exist for n=3,9,11,17,27 and may exist for other n > 27.
For those n for which a proven factorization exists, b=1 results in a prime of the form n+2.
|
|
LINKS
|
|
|
EXAMPLE
|
a(6)=448 because 448 is the smallest number b such that 1 + Sum_{k=0..6} b^(2^k) is prime.
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,hard,more
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|