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Search: id:A087156
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| A087156 |
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Nonnegative numbers excluding 1. |
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+0
6
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| 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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The old entry with this sequence number was a duplicate of A026835.
A063524(a(n)) = 0. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 11 2008]
Inverse binomial transform of A006589 . [From Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Nov 25 2008]
a(n) = maximum value of j, where 1 <= j <= n-1, such that floor(j^2 / n) > 0 for each n.
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FORMULA
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G.f.: x^2*(2-x)/(1-x)^2 . E.g.f.: x*(exp(x)-1). [From Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Nov 25 2008]
a(n)=A163300(n)/2. [From Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Aug 14 2009]
a(n)=n-1+[(n+1) mod n], with n>=1 [From Paolo P. Lava (ppl(AT)spl.at), Nov 06 2009]
a(n)=n mod sigma_k(n), where sigma_k is the k divisor sigma function [From Barbarel Tres Mil (barbarel3000(AT)yahoo.es), Nov 11 2009]
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MATHEMATICA
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A087156[n_] := Mod[n, DivisorSigma[1, n]] [From Barbarel Tres Mil (barbarel3000(AT)yahoo.es), Nov 11 2009]
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CROSSREFS
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Cf. A000027.
Cf. A166373.
Sequence in context: A131738 A000027 A001477 this_sequence A033619 A130734 A090108
Adjacent sequences: A087153 A087154 A087155 this_sequence A087157 A087158 A087159
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KEYWORD
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nonn,new
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Oct 11 2008
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EXTENSIONS
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Comment and cross-reference added by Christopher Hunt Gribble (chris.eveswell(AT)virgin.net), Oct 14 2009, Oct 17 2009
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