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URL: https://oeis.org/A105869

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A105869
Numbers k such that sigma(k) == 10 (mod k).
1
1, 14, 40, 1696, 518656, 34358296576
OFFSET
1,2
COMMENTS
a(7) > 10^13. - Giovanni Resta, Apr 02 2014
No other terms < 1.5*10^14. - Jud McCranie, Jun 02 2019
9671406556892844141838336 is a term (as are all numbers of the form 2^(j-1)*(2^j - 11) where 2^j - 11 is prime). - Jon E. Schoenfield, Jun 02 2019
EXAMPLE
Sigma(40) = 90 == 10 (mod 40).
MATHEMATICA
Join[{1}, Select[Range[600000], Mod[DivisorSigma[1, #], #]==10 &]] (* Vincenzo Librandi, Mar 11 2014 *)
CROSSREFS
Sequence in context: A124707 A126368 A125816 * A216298 A056034 A039404
KEYWORD
more,nonn
AUTHOR
Shyam Sunder Gupta, May 05 2005
EXTENSIONS
Initial term 1 added by Vincenzo Librandi, Mar 11 2014
a(6) from Giovanni Resta, Apr 02 2014
STATUS
approved