

A328951


Numbers m such that sigma(m) + tau(m) = 3m.


0




OFFSET

1,1


COMMENTS

Abundant numbers m with abundance A(m) = m  tau(m) = A049820(m), where A049820(n) is the number of nondivisors of n .
Subsequence of A056076.
Corresponding values of A(m) = m  tau(m): 48, 5436, 2500632, ...
Number 4 is the only number m with deficiency D(m) = m  tau(m).
10^13 < a(4) <= 24361213461200. 808989640739424 is also a term.  Giovanni Resta, Nov 14 2019


LINKS

Table of n, a(n) for n=1..3.


EXAMPLE

Number 60 is in the sequence because sigma(60) + tau(60) = 3*60; 168 + 12 = 180 = 3*60.


MATHEMATICA

Select[Range[3*10^6], DivisorSigma[0, #] + DivisorSigma[1, #] == 3# &] (* Amiram Eldar, Nov 10 2019 *)


PROG

(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


CROSSREFS

Cf. A000005, A000203, A033880, A049820, A056076.
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)).
Sequence in context: A084274 A289307 A091032 * A178785 A091753 A303790
Adjacent sequences: A328948 A328949 A328950 * A328952 A328953 A328954


KEYWORD

nonn,bref,more


AUTHOR

Jaroslav Krizek, Nov 10 2019


STATUS

approved



