

A055153


Numbers n such that sigma(n) = 7n/2.


13



4320, 4680, 26208, 20427264, 197064960, 21857648640, 57575890944, 88898072401645056, 301183421949935616, 9083288595228991885541376, 22290964134962716779872256, 230361837156847526055247872
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OFFSET

1,1


COMMENTS

This sequence also contains the term 230361837156847526055247872.  Yasutoshi Kohmoto, May 10 2008
301183421949935616 also belongs to this sequence.  Avinoam Kalma (a.kalma(AT)gmail.com), May 04 2009
22290964134962716779872256 is in this sequence. [From Gerard P. Michon, May 10 2009]


LINKS



EXAMPLE

Sigma(4320)=15120=7*4320/2, so 4320 is in the sequence.


MAPLE

with(numtheory); P:=proc(i) local n; for n from 1 by 1 to i do if sigma(n)/n=7/2 then; print(n); fi; od; end: P(100000000) # Paolo P. Lava, Sep 18 2008


MATHEMATICA

Do[If[DivisorSigma[1, m]==3.5*m, Print[m]], {m, 2*10^8}]


PROG



CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS

a(8), a(10), a(12) [and above] found by Michel Marcus, added by Gerard P. Michon, Jun 04 2009


STATUS

approved



