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A071817
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Number of 3-digit numbers whose digits add up to n.
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10
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1, 3, 6, 10, 15, 21, 28, 36, 45, 54, 61, 66, 69, 70, 69, 66, 61, 54, 45, 36, 28, 21, 15, 10, 6, 3, 1
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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The sequence as a whole is palindromic; a(n) = a(28-n). - Jon E. Schoenfield, Nov 19 2016
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LINKS
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Table of n, a(n) for n=1..27.
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FORMULA
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G.f.: (1 - x^10)^2*(x - x^10)/(1 - x)^3. - Miquel Cerda, Jul 09 2017
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EXAMPLE
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a(4) = 10 because there are 10 different 3-digit numbers whose digit sum is 4 (103, 112, 121, 130, 202, 211, 220, 301, 310, 400, which are the 3-digit elements of A052218).
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MAPLE
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for i from 1 to 9*3 do a[i] := 0:od:for i from 100 to 999 dob := convert(i, base, 10): s := sum(b[j], j=1..nops(b)):a[s] := a[s]+1:od:seq(a[j], j=1..3*9);
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CROSSREFS
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Cf. A071816.
Sequence in context: A062918 A113168 A341192 * A033442 A105335 A130489
Adjacent sequences: A071814 A071815 A071816 * A071818 A071819 A071820
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KEYWORD
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fini,full,nonn,base
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AUTHOR
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Graeme McRae, Jun 07 2002
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EXTENSIONS
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Corrected and extended by Sascha Kurz, Feb 07 2003
Name clarified by Jon E. Schoenfield, Nov 20 2016
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STATUS
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approved
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