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 A274552 Numbers n such that sigma(n) == 0 (mod n-3). 2
 4, 5, 6, 7, 8, 15, 52, 315, 592, 1155, 2102272, 815634435 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE sigma(4) mod 4-3 = 7 mod 1 = 0. MAPLE with(numtheory); P:=proc(q, h) local n;  for n from 1 to q do if n+h>0 then if type(sigma(n)/(n+h), integer) then print(n); fi; fi; od; end: P(10^9, -3); MATHEMATICA k = -3; Select[Range[Abs@ k + 1, 10^6], Mod[DivisorSigma[1, #], # + k] == 0 &] (* Michael De Vlieger, Jul 01 2016 *) PROG (MAGMA) [n: n in [4..2*10^6] | SumOfDivisors(n) mod (n-3) eq 0 ]; // Vincenzo Librandi, Jul 02 2016 (PARI) is(n) = if(n < 4, return(0), Mod(sigma(n), n-3)==0) \\ Felix FrÃ¶hlich, Jul 02 2016 CROSSREFS Cf. A067702, A087485, A141548, A274551, A274553-A274566. Sequence in context: A285218 A059709 A071623 * A280682 A140293 A075341 Adjacent sequences:  A274549 A274550 A274551 * A274553 A274554 A274555 KEYWORD nonn,more AUTHOR Paolo P. Lava, Jun 28 2016 EXTENSIONS a(11)-a(12) from Giovanni Resta STATUS approved

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Last modified March 29 13:55 EDT 2020. Contains 333107 sequences. (Running on oeis4.)