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Numbers k such that sigma(k) == 10 (mod k).
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%I #20 Jun 02 2019 23:38:56

%S 1,14,40,1696,518656,34358296576

%N Numbers k such that sigma(k) == 10 (mod k).

%C a(7) > 10^13. - _Giovanni Resta_, Apr 02 2014

%C No other terms < 1.5*10^14. - _Jud McCranie_, Jun 02 2019

%C 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

%e Sigma(40) = 90 == 10 (mod 40).

%t Join[{1}, Select[Range[600000], Mod[DivisorSigma[1, #], #]==10 &]] (* _Vincenzo Librandi_, Mar 11 2014 *)

%K more,nonn

%O 1,2

%A _Shyam Sunder Gupta_, May 05 2005

%E Initial term 1 added by _Vincenzo Librandi_, Mar 11 2014

%E a(6) from _Giovanni Resta_, Apr 02 2014