|
| |
|
|
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
| 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 * A194330 A194286 A063473
Adjacent sequences: A090869 A090870 A090871 * A090873 A090874 A090875
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Farideh Firoozbakht (f.firoozbakht(AT)sci.ui.ac.ir), Jan 31 2004
|
|
|
EXTENSIONS
| a(6) from Jens Kruse Andersen (jens.k.a(AT)get2net.dk), May 06 2007
|
| |
|
|
