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A001212
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a(n) = solution to the postage stamp problem with n denominations and 2 stamps.
(Formerly M1089 N0972)
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28
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2, 4, 8, 12, 16, 20, 26, 32, 40, 46, 54, 64, 72, 80, 92, 104, 116, 128, 140, 152, 164, 180, 196, 212
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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Fred Lunnon [W. F. Lunnon] defines "solution" to be the smallest value not obtainable by the best set of stamps. The solutions given are one lower than this, that is, the sequence gives the largest number obtainable without a break using the best set of stamps.
a(20)=152: There is only one set of 20 denominations covering all sums through 152: {1, 3, 4, 5, 8, 14, 20, 26, 32, 38, 44, 50, 56, 62, 68, 71, 72, 73, 75, 76}. - Tim Peters (tim.one(AT)comcast.net), Oct 04 2006
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REFERENCES
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Gardner, M. The Sixth Book of Mathematical Games from Scientific American. Chicago, IL: University of Chicago Press, p. 115 (Coins of the Realm), 1984.
R. K. Guy, Unsolved Problems in Number Theory, C12.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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F. H. Kierstead, Jr.,, The Stamp Problem, J. Rec. Math., Vol. ?, Year ?, page 298. [Annotated and scanned copy]
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CROSSREFS
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A row or column of the array A196416 (possibly with 1 subtracted from it).
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KEYWORD
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nonn,nice,more
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AUTHOR
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EXTENSIONS
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Corrected a(17). Added a(18) and a(19) from Challis. - R. J. Mathar, Apr 01 2006
Entry improved by comments from John Seldon (johnseldon(AT)onetel.com), Sep 15 2004
a(20) from Tim Peters (tim.one(AT)comcast.net), Oct 04 2006
Added terms a(21) and a(22) from Challis and Robinson. John P Robinson (john-robinson(AT)uiowa.edu), Feb 19 2010
Added term a(23) from Challis and Robinson's July 2013 addendum, by Jukka Kohonen, Oct 25 2013
Added a(24) from Kohonen and Corander (2013). - N. J. A. Sloane, Jan 08 2014
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STATUS
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approved
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