|
Search: id:A073936
|
|
|
| A073936 |
|
2^n + 1 is squarefree and has exactly 2 prime factors. |
|
+0
3
|
|
| 5, 6, 7, 11, 12, 13, 17, 19, 20, 23, 28, 31, 32, 40, 43, 61, 64, 79, 92, 101, 104, 127, 128, 148, 167, 191, 199
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
LINKS
|
AMS Books Online, Factorizations of b^n = +-1, b=2,3,5,6,7,10,11,12 Up to High Powers, Third Edition
Arjen Bot, Factors for 2^n-1 and 2^n+1 for 1200 < n < 10000
|
|
FORMULA
|
Solutions to A000005[A000051(x)]=4 or A046798[x]=4
|
|
EXAMPLE
|
11 is a member because 1+2^11=2049=3.683.
|
|
MATHEMATICA
|
Do[ If[ Length[ Divisors[1 + 2^n]] == 4, Print[n]], {n, 1, 200}]
|
|
CROSSREFS
|
Cf. A000005, A000051, A046798. Different from A066263.
Sequence in context: A131503 A047266 A026309 this_sequence A064615 A139205 A039589
Adjacent sequences: A073933 A073934 A073935 this_sequence A073937 A073938 A073939
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Labos E. (labos(AT)ana.sote.hu), Aug 13 2002
|
|
EXTENSIONS
|
Edited by Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 19 2002
|
|
|
Search completed in 0.002 seconds
|
