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Search: id:A058971
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| A058971 |
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For a rational number p/q let f(p/q) = sum of divisors of p+q divided by number of divisors of p+q; a(n) is obtained by iterating f, starting at n/1, until an integer is reached, or if no integer is ever reached then a(n) = 0. |
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+0
8
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| 3, 2, 6, 3, 3, 4, 10, 87, 6, 6, 9, 7, 6, 6, 87, 9, 6, 10, 7, 8, 9, 12, 9, 15, 12, 10, 16, 15, 9, 16, 12, 12, 15, 12, 87, 19, 15, 14, 19, 21, 12, 22, 14, 13, 18, 24, 34, 19, 12, 18, 0, 27, 15, 18, 15, 20, 24, 30, 14, 31, 24, 18, 51, 21, 18, 34, 21, 24, 18, 36, 24, 37, 30, 21, 37
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Matthew M. Conroy, Home page (listed instead of email address)
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EXAMPLE
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1 -> (1+2)/2 = 3/2 -> (1+5)/2 = 3, so a(1) = 3. 51 -> 49/3 -> 49/3 -> ..., so a(51) = 0.
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MAPLE
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with(numtheory); f := proc(n) if whattype(n) = integer then sigma(n+1)/sigma[0](n+1) else sigma(numer(n)+denom(n))/sigma[0](numer(n)+denom(n)); fi; end;
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CROSSREFS
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Cf. A058972, A058977.
Sequence in context: A078589 A077880 A131969 this_sequence A137324 A011209 A071018
Adjacent sequences: A058968 A058969 A058970 this_sequence A058972 A058973 A058974
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KEYWORD
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nonn,easy,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Jan 14 2001
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EXTENSIONS
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More terms from Matthew M. Conroy, Apr 18 2001, who remarks that a(51) = a(655) = a(1039) = 0 are all the zeros of a(n) for n<10^5.
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