|
|
A135627
|
|
Perfect numbers minus 1.
|
|
5
|
|
|
5, 27, 495, 8127, 33550335, 8589869055, 137438691327, 2305843008139952127, 2658455991569831744654692615953842175, 191561942608236107294793378084303638130997321548169215
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
Conjecture: every odd prime is a factor of at least one number in this sequence. - J. Lowell, Apr 17 2014
a(n) written in base 2 is A138831(n) which is also a member of A138148 (cyclops numbers with binary digits only), assuming there are no odd perfect numbers. - Omar E. Pol, Oct 24 2016 [clarified on Nov 03 2018].
|
|
LINKS
|
|
|
FORMULA
|
|
|
MATHEMATICA
|
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|