A274556 - OEIS

%I #24 Sep 08 2022 08:46:17

%S 6,7,8,11,12,18,21,26,68,656,2336,8768,133376,528896,34360918016

%N Numbers k such that sigma(k) == 0 (mod k-5).

%C A101223 is a subset of this sequence.

%e sigma(6) (mod 6-5) = 12 mod 1 = 0.

%p with(numtheory); P:=proc(q,h) local n;  for n from 1 to q do

%p if n+h>0 then if type(sigma(n)/(n+h),integer) then print(n); fi; fi; od; end: P(10^9,-5);

%t n = -5; Select[Range[Abs@ n + 1, 10^6], Mod[DivisorSigma[1, #], # + n] == 0 &] (* _Michael De Vlieger_, Jul 01 2016 *)

%o (Magma) [n: n in [6..2*10^6] | SumOfDivisors(n) mod (n-5) eq 0]; // _Vincenzo Librandi_, Jul 02 2016

%Y Cf. A067702, A101223, A223609, A274551-A274554.

%K nonn,more

%O 1,1

%A _Paolo P. Lava_, Jun 30 2016

%E a(15) from _Giovanni Resta_, Jul 01 2016