|
|
A175906
|
|
Numbers n of the form 2^(A000043-1)*A046528 such that sigma(n) is perfect number.
|
|
0
|
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
sigma(sigma(A046528(2,12,13,18,21,22,56,57,175,176,177,..))) is Mersenne prime.
|
|
LINKS
|
|
|
FORMULA
|
a(n)= 2^( A000043(2,5,5,6,7,7,8,8,9,9,9,..)-1)*A046528(2,12,13,18,21,22,56,57,175,176,177,..).
|
|
EXAMPLE
|
45091651584=2^18*3*7*8191, sigma(45091651584)=137438691328 is perfect number.
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|