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Message boards : General discussion : Sme question associated with function sigma(n)

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Svetlana U.

Joined: 21 Apr 13
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Message 71313 - Posted: 10 Dec 2013 | 11:13:05 UTC

Does anybody know the answer on some questions associated with A231484?

1. Does there exists an odd number n > 1 for which sigma(n),
sigma(sigma(n)) and sigma(sigma(sigma(n))) are odd too?

2. Does there exists a number n > 1 such that sigma(sigma(sigma(n)))/n < 1.5?

3. Note that sigma(3^4) = 11^2. Does there exists another pair (p,r)
such that p is prime, r > 1 and sigma(p^r) = q^s where q is prime and
s > 1?

serge

Joined: 21 Jun 12
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Message 71320 - Posted: 10 Dec 2013 | 16:43:58 UTC - in response to Message 71313.

You could ask at NMBRTHRY list. (google it)
____________
My lucky number is Phi(4, 2^2396029-1)/2.

Message boards : General discussion : Sme question associated with function sigma(n)