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A046986 Multiply perfect numbers whose average divisor divides the number but is not an integer. 2
28, 496, 8128, 2178540, 33550336, 142990848, 459818240, 1379454720, 8589869056, 43861478400, 66433720320, 137438691328, 704575228896, 181742883469056, 6088728021160320, 14942123276641920, 20158185857531904 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..17.

FORMULA

a=s1/s0, b=x/a, c=s1/x where s1 is the sum and s0 is the number of divisors of x. Here a is not but b and c are integers.

EXAMPLE

x=21785540, d[ x ]=s0=216 and Sigma[ 1,x ]=8714160. The three quotients are a=40343.334 is not an integer but b=54 and c=4 are integers.

CROSSREFS

In A007691 and A001599 but not in A003601. Cf. A046985, A046987.

Sequence in context: A079598 A212302 A046999 * A323747 A028145 A028167

Adjacent sequences:  A046983 A046984 A046985 * A046987 A046988 A046989

KEYWORD

nonn

AUTHOR

Labos Elemer

EXTENSIONS

a(12)-a(17) from Donovan Johnson, Nov 30 2008

STATUS

approved

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Last modified August 20 07:48 EDT 2019. Contains 326143 sequences. (Running on oeis4.)