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%I #22 Sep 08 2022 08:46:17
%S 4,5,6,7,8,15,52,315,592,1155,2102272,815634435
%N Numbers k such that sigma(k) == 0 (mod k-3).
%e sigma(4) mod (4-3) = 7 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,-3);
%t k = -3; Select[Range[Abs@ k + 1, 10^6], Mod[DivisorSigma[1, #], # + k] == 0 &] (* _Michael De Vlieger_, Jul 01 2016 *)
%o (Magma) [n: n in [4..2*10^6] | SumOfDivisors(n) mod (n-3) eq 0 ]; // _Vincenzo Librandi_, Jul 02 2016
%o (PARI) is(n) = if(n < 4, return(0), Mod(sigma(n), n-3)==0) \\ _Felix Fröhlich_, Jul 02 2016
%Y Cf. A000203, A067702, A087485, A141548, A274551, A274553-A274566.
%K nonn,more
%O 1,1
%A _Paolo P. Lava_, Jun 28 2016
%E a(11)-a(12) from _Giovanni Resta_
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