A327158 - OEIS

A327158

Unitary multiply-perfect numbers: n divides usigma(n), where usigma is the sum of unitary divisors of n (A034448).

1, 6, 60, 90, 87360

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OFFSET

1,2

COMMENTS

10^13 < a(6) <= 146361946186458562560000. - Giovanni Resta, Aug 29 2019

LINKS

Peter Hagis, Jr., Lower bounds for unitary multiperfect numbers, Fibonacci Quarterly, Vol. 22, No. 2 (1984), pp. 140-143.

PROG

(PARI)

A034448(n) = { my(f=factorint(n)); prod(k=1, #f~, 1+(f[k, 1]^f[k, 2])); }; \\ After code in A034448

isA327158(n) = (gcd(n, A034448(n))==n);

CROSSREFS

Fixed points of A323166, positions of zeros in A327164.

Cf. A002827 (a subsequence), A034448, A327163.

Cf. also A007691.

KEYWORD

nonn,more

AUTHOR

STATUS

approved