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Search: id:A002961
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| A002961 |
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Numbers n such that n and n+1 have same sum of divisors.
(Formerly M4950)
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+0
18
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| 14, 206, 957, 1334, 1364, 1634, 2685, 2974, 4364, 14841, 18873, 19358, 20145, 24957, 33998, 36566, 42818, 56564, 64665, 74918, 79826, 79833, 84134, 92685, 109214, 111506, 116937, 122073, 138237, 147454, 161001, 162602, 166934
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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For the values of n < 2*10^10 in this sequence, sigma(n)/n is between 1.5 and 2.25. - T. D. Noe, Sep 17 2007
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REFERENCES
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M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 840.
W. Sierpi\'{n}ski, A Selection of Problems in the Theory of Numbers. Macmillan, NY, 1964, p. 110.
R. K. Guy, Unsolved Problems in Theory of Numbers, Sect. B13.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..1378
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, December 1972 [alternative scanned copy].
Lourdes Benito, Solutions of the problem of Erdos-Sierpinski: sigma(n)=sigma(n+1)
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MAPLE
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with(numtheory); P:=proc(n) local a, i; for i from 1 by 1 to n do a:=sigma(i)/sigma(i+1); if a=1 then print(i); fi; od; end: P(100000); - Paolo P. Lava (ppl(AT)spl.at), Aug 23 2007
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CROSSREFS
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A000203 (sigma function), A053215, A053249, A054004
Sequence in context: A068769 A113349 A109764 this_sequence A063071 A097261 A097183
Adjacent sequences: A002958 A002959 A002960 this_sequence A002962 A002963 A002964
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KEYWORD
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nonn,nice
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AUTHOR
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njas, Mira Bernstein, Robert G. Wilson v (rgwv(AT)rgwv.com)
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EXTENSIONS
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More terms from j.mccranie(AT)comcast.net (Jud Mccranie) (10/97)
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