OFFSET
1,1
COMMENTS
Conjectured finite and probably these are the only terms; cf. Flammenkamp's link. [Georgi Guninski, Jul 25 2012]
LINKS
T. D. Noe, Table of n, a(n) for n = 1..65 (complete sequence from Flammenkamp)
F. Firoozbakht, M. F. Hasler, Variations on Euclid's formula for Perfect Numbers, JIS 13 (2010) #10.3.1
Achim Flammenkamp, The Multiply Perfect Numbers Page
Fred Helenius, Link to Glossary and Lists
Walter Nissen, Abundancy : Some Resources
Eric Weisstein's World of Mathematics, Multiperfect Number.
EXAMPLE
From Daniel Forgues, May 09 2010: (Start)
14182439040 = 2^7*3^4*5*7*11^2*17*19
sigma(14182439040) = (2^8-1)/1*(3^5-1)/2*(5^2-1)/4*(7^2-1)/6*(11^3-1)/10*(17^2-1)/16*(19^2-1)/18
= (255)*(121)*(6)*(8)*(133)*(18)*(20)
= (3*5*17)*(11^2)*(2*3)*(2^3)*(7*19)*(2*3^2)*(2^2*5)
= 2^7*3^4*5^2*7*11^2*17*19
= (5) * (2^7*3^4*5*7*11^2*17*19)
= 5 * 14182439040 (End)
PROG
(PARI) is(n)=sigma(n)==5*n \\ Charles R Greathouse IV, Apr 05 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved