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A046985
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Multiply perfect numbers whose average divisor is an integer and divides the number itself.
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9
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1, 6, 672, 30240, 32760, 23569920, 45532800, 14182439040, 51001180160, 153003540480, 403031236608, 13661860101120, 154345556085770649600, 9186050031556349952000, 143573364313605309726720
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OFFSET
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1,2
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COMMENTS
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sigma_0(n) is the number of divisors of n (A000005).
sigma_1(n) is the sum of the divisors of n [same as sigma(n)] (A000203).
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LINKS
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FORMULA
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a=s1/s0, b=(k*s0)/s1 and c=s1/k, where s1=sigma_1(k), s0=sigma_0(k), the sum and number of divisors of k; a, b, c are integers.
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EXAMPLE
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x=45532800, sigma_0=384, sigma_1=182131200. The three quotients are as follows: a=474300, b=96 and c=4.
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PROG
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(PARI) isok(n) = s1 = sigma(n); s0 = numdiv(n); !(s1 % n) && !(s1 % s0) && !((n*s0) % s1); \\ Michel Marcus, Dec 10 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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