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A142717
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First (leftmost) odd term in the n-th row of triangle A120070.
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4
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3, 5, 15, 21, 35, 45, 63, 77, 99, 117, 143, 165, 195, 221, 255, 285, 323, 357, 399, 437, 483, 525, 575, 621, 675, 725, 783, 837, 899, 957, 1023, 1085, 1155, 1221, 1295, 1365, 1443, 1517, 1599, 1677, 1763, 1845, 1935, 2021, 2115, 2205, 2303, 2397, 2499, 2597
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OFFSET
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1,1
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COMMENTS
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Also: Records sequence of A100181.
The last (rightmost) term in the n-th row of triangle A120070 is A005408(n).
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LINKS
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Table of n, a(n) for n=1..50.
Index entries for linear recurrences with constant coefficients, signature (2, 0, -2, 1).
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FORMULA
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First differences: a(n+1)-a(n)=A142954(n).
a(n)=(n+1)^2-1 =A000466((n+1)/2) if n odd. a(n)= (n+1)^2-4 =A078371(n/2-1) if n even. a(n) = 2*a(n-1) -2*a(n-3) +a(n-4). G.f.: x(3-x+5x^2-3x^3)/((1+x)(1-x)^3). - R. J. Mathar, Oct 24 2008
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EXAMPLE
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The odd terms of A120070 build the irregular triangle
3;
5;
15,7;
21,9;
35,27,11;
45,33,13;
63,55,39,15;
The leftmost column defines this sequence.
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CROSSREFS
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Sequence in context: A201874 A059528 A070079 * A057742 A201433 A101129
Adjacent sequences: A142714 A142715 A142716 * A142718 A142719 A142720
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KEYWORD
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nonn
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AUTHOR
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Paul Curtz, Sep 26 2008
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EXTENSIONS
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Edited and extended by R. J. Mathar, Oct 24 2008
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STATUS
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approved
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