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

Offset

1,2

Comments

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

Links

Table of n, a(n) for n=1..5.

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.

Sequence in context: A331108 A324707 A007357 * A002827 A331111 A324199

Adjacent sequences: A327155 A327156 A327157 * A327159 A327160 A327161

Keyword

nonn,more

Author

Antti Karttunen, Aug 28 2019

Status

approved