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A328951
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Numbers m such that sigma(m) + tau(m) = 3m.
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0
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OFFSET
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1,1
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COMMENTS
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Abundant numbers m with abundance A(m) = m - tau(m) = A049820(m), where A049820(n) is the number of non-divisors of n.
Corresponding values of A(m) = m - tau(m): 48, 5436, 2500632, ...
4 is the only number m with deficiency D(m) = m - tau(m).
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LINKS
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EXAMPLE
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60 is a term because sigma(60) + tau(60) = 3*60; 168 + 12 = 180 = 3*60.
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MATHEMATICA
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Select[Range[3*10^6], DivisorSigma[0, #] + DivisorSigma[1, #] == 3# &] (* Amiram Eldar, Nov 10 2019 *)
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PROG
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(Magma) [m: m in [1..10^7] | SumOfDivisors(m) - 2*m eq m - NumberOfDivisors(m)];
(PARI) isok(m) = my(f=factor(m)); sigma(f) + numdiv(m) == 3*m; \\ Michel Marcus, Nov 13 2019
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CROSSREFS
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Cf. A083874 (numbers m such that sigma(m) + tau(m) = 2m).
Cf. A011251 (numbers m such that sigma(m) + phi(m) = 3m).
Cf. A329104 (numbers m with abundance A(m) = tau(m)).
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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