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Sum of divisors of the multiply-perfect numbers.
3

%I #15 May 12 2024 00:46:11

%S 1,12,56,360,992,2016,16256,120960,131040,1571328,8714160,94279680,

%T 67100672,182131200,571963392,1379454720,5517818880,4428914688,

%U 17179738112,70912195200,159991977600,175445913600,153003540480,265734881280,274877382656,612014161920

%N Sum of divisors of the multiply-perfect numbers.

%C When sorted, this is A081756. - _N. J. A. Sloane_, May 03 2019

%H Amiram Eldar, <a href="/A307741/b307741.txt">Table of n, a(n) for n = 1..730</a>

%F a(n) = sigma(A007691(n)) = A000203(A007691(n)).

%F a(n) = A007691(n) * A054030(n).

%e For n = 3; a(3) = sigma(A007691(3)) = sigma(28) = 56.

%o (Magma) [SumOfDivisors(n): n in [1..1000000] | IsIntegral(SumOfDivisors(n)/n)]

%o (PARI) lista(nn) = {for (n=1, nn, my(s=sigma(n)); if (! (s % n), print1(s, ", ")););} \\ _Michel Marcus_, Apr 26 2019

%Y Cf. A000203, A007691, A054030, A088843 (tau(A007691)), A139256.

%Y See also A081756.

%K nonn

%O 1,2

%A _Jaroslav Krizek_, Apr 26 2019