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Search: id:A030057
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| A030057 |
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Least number which is not a sum of distinct divisors of n. |
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+0
3
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| 2, 4, 2, 8, 2, 13, 2, 16, 2, 4, 2, 29, 2, 4, 2, 32, 2, 40, 2, 43, 2, 4, 2, 61, 2, 4, 2, 57, 2, 73, 2, 64, 2, 4, 2, 92, 2, 4, 2, 91, 2, 97, 2, 8, 2, 4, 2, 125, 2, 4, 2, 8, 2, 121, 2, 121, 2, 4, 2, 169, 2, 4, 2, 128, 2, 145, 2, 8, 2, 4, 2, 196, 2, 4, 2, 8, 2, 169, 2, 187, 2, 4, 2, 225, 2, 4, 2, 181
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(n)=2 if and only if n is odd. a(2^n)=2^(n+1). - Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 07 2005
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LINKS
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David Wasserman (dwasserm(AT)earthlink.net), Apr 24 2007, Table of n, a(n) for n = 1..1000
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EXAMPLE
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a(10)=4 because 4 is the least positive integer that is not a sum of distinct divisors (namely 1,2,5 and 10) of 10.
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MAPLE
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with(combinat): with(numtheory): for n from 1 to 100 do div:=powerset(divisors(n)): b[n]:=sort({seq(sum(div[i][j], j=1..nops(div[i])), i=1..nops(div))}) od: for n from 1 to 100 do B[n]:={seq(k, k=0..1+sigma(n))} minus b[n] od: seq(B[n][1], n=1..100); (Deutsch)
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CROSSREFS
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Cf. A005153, A093896.
Sequence in context: A073017 A059866 A093895 this_sequence A134066 A090988 A095728
Adjacent sequences: A030054 A030055 A030056 this_sequence A030058 A030059 A030060
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KEYWORD
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nonn,nice
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AUTHOR
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David W. Wilson (davidwwilson(AT)comcast.net)
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EXTENSIONS
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Edited by N. J. A. Sloane (njas(AT)research.att.com), May 05 2007
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