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 A046061 6-multiperfect numbers. 21
 154345556085770649600, 9186050031556349952000, 680489641226538823680000, 6205958672455589512937472000, 13297004660164711617331200000, 15229814702070563916152832000 (list; graph; refs; listen; history; text; internal format)
 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..245 (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) 154345556085770649600 = 2^15*3^5*5^2*7^2*11*13*17*19*31*43*257 sigma(154345556085770649600) = (2^16-1)/1*(3^6-1)/2*(5^3-1)/4*(7^3-1)/6*(11^2-1)/10*(13^2-1)/12*(17^2-1)/16*(19^2-1)/18*(31^2-1)/30*(43^2-1)/42*(257^2-1)/256 = 65535*364*31*57*12*14*18*20*32*44*258 = (5*3*17*257)*(2^2*7*13)*(31)*(3*19)*(2^2*3)*(2*7)*(2*3^2)*(2^2*5)*(2^5)*(2^2*11)*(2*3*43) = 2^16*3^6*5^2*7^2*11*13*17*19*31*43*257 = (2*3) * (2^15*3^5*5^2*7^2*11*13*17*19*31*43*257) = 6 * 154345556085770649600 (End) PROG (PARI) is(n)=sigma(n)==6*n \\ Charles R Greathouse IV, Apr 05 2013 CROSSREFS Cf. A000396, A005820, A027687, A046060, A007539. Sequence in context: A290156 A095436 A247262 * A181790 A252504 A239924 Adjacent sequences:  A046058 A046059 A046060 * A046062 A046063 A046064 KEYWORD nonn AUTHOR STATUS approved

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Last modified September 18 23:30 EDT 2020. Contains 337175 sequences. (Running on oeis4.)