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A234516
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Composite numbers n sorted by decreasing values of alpha(n) = log_n(sigma(n)) - log_n(n+1), where sigma(n) = A000203(n) = the sum of divisors of n.
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12
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12, 6, 24, 36, 18, 30, 60, 8, 4, 48, 20, 72, 120, 84, 16, 42, 10, 40, 180, 90, 96, 144, 240, 168, 108, 360, 28, 54, 420, 252, 132, 80, 216, 210, 32, 126, 300, 336, 480, 56, 192, 288, 720, 840, 66, 504, 156, 540, 150, 264, 14, 600, 140, 270, 1260, 432, 78, 1080
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OFFSET
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1,1
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COMMENTS
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The number alpha(n) = log_n(sigma(n)) - log_n(n+1) = log_n[sigma(n) / (n+1)] is called the alpha-deviation from primality of number n; alpha(p) = 0 for p = prime. See A234520 for definition of beta(n).
Lim_n->infinity alpha(n) = 0.
Conjecture: Every composite number n has a unique value of alpha(n).
Conjecture: sequence A234517 is not the sequence of numbers from a(n) such that a(n) > a(k) for all k < n.
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LINKS
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EXAMPLE
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For the number 12; alpha(12) = log_12(sigma(12)) - log_12(12+1) = log_12(28) - log_12(13) = 0.308766187… = A234518 (maximal value of function alpha(n)).
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PROG
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(PARI) lista(nn) = {v = vector(nn, n, if ((n==1) || isprime(n), 0, log(sigma(n)/(n+1))/log(n))); v = vecsort(v, , 5); for (i=1, 80, print1(v[i], ", ")); } \\ Michel Marcus, Dec 10 2014
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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