|
| |
|
|
A090872
|
|
a(n) is the smallest number m greater than 1 such that m^(2^k)+1 for k=0,1,...,n are primes.
|
|
4
|
| |
|
|
|
OFFSET
|
0,1
|
|
|
COMMENTS
|
The first five terms of this sequence correspond to Fermat primes.
|
|
|
LINKS
|
Table of n, a(n) for n=0..6.
C. Rivera, Puzzle 137. Product of primes + 1, a square.
C. Rivera (ed.), Prime Puzzle # 399.
|
|
|
EXAMPLE
|
a(5)=7072833120 because 7072833120^2^k+1 for k=0,1,2,3,4,5 are primes.
|
|
|
CROSSREFS
|
Cf. A019434, A000215.
Cf. A090873-A090875.
Sequence in context: A056993 A057331 A067089 * A225538 A212355 A194330
Adjacent sequences: A090869 A090870 A090871 * A090873 A090874 A090875
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
Farideh Firoozbakht, Jan 31 2004
|
|
|
EXTENSIONS
|
a(6) from Jens Kruse Andersen, May 06 2007
|
|
|
STATUS
|
approved
|
| |
|
|
