cp's OEIS Frontend

A283565 Numbers n such that n = Sum_{k=1..m} (n mod k) for some m.

%I A283565 #11 Mar 11 2017 21:20:31
%S A283565 0,1,2,7,8,9,10,13,15,19,22,23,25,31,37,49,51,52,57,72,95,98,100,133,
%T A283565 140,146,152,158,168,189,196,212,315,348,376,383,396,407,416,451,452,
%U A283565 497,521,541,548,551,568,583,586,592,593,657,663,683,729,780,784,794
%N A283565 Numbers n such that n = Sum_{k=1..m} (n mod k) for some m.
%C A283565 A283593 gives the least m > 0 as described in the name.
%C A283565 Numbers t such that t and 2*t are both in this sequence are 0, 1, 49, 98, 1249, 2599, 3784, 9565, 10933, ... - _Altug Alkan_, Mar 11 2017
%H A283565 Rémy Sigrist, <a href="/A283565/b283565.txt">Table of n, a(n) for n = 1..10000</a>
%e A283565 (7 mod 1) + (7 mod 2) + (7 mod 3) + (7 mod 4) + (7 mod 5) = 0 + 1 + 1 + 3 + 2 = 7, hence 7 appears in this sequence.
%e A283565 (4 mod 1) + (4 mod 2) + (4 mod 3) + (4 mod 4) = 0 + 0 + 1 + 0 = 1, and (4 mod 1) + (4 mod 2) + (4 mod 3) + (4 mod 4) + (4 mod 5) = 0 + 0 + 1 + 0 + 4 = 5, hence 4 does not appear in this sequence.
%o A283565 (PARI) isok(n) = my (s=0); my (k=1); while (s<n, s += n%k; k++); return (s==n)
%Y A283565 Cf. A004125, A283593.
%K A283565 nonn
%O A283565 1,3
%A A283565 _Rémy Sigrist_, Mar 11 2017