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A124072
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First differences of A129819.
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3
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0, 1, 0, 2, 1, 3, 1, 4, 2, 5, 2, 6, 3, 7, 3, 8, 4, 9, 4, 10, 5, 11, 5, 12, 6, 13, 6, 14, 7, 15, 7, 16, 8, 17, 8, 18, 9, 19, 9, 20, 10, 21, 10, 22, 11, 23, 11, 24, 12, 25, 12, 26
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| A129819 and its repeated differences are
0.0.1..1..3..4..7...8..12..14.19..21.27....
..0.1..0..2..1..3...1...4...2..5...2..6....
....1.-1..2.-1..2..-2...3..-2..3..-3..4....
......-2..3.-3..3..-4...5..-5..5..-6..7....
..........5.-6..6..-7...9.-10.10.-11.13...
...........-11.12.-13..16.-19.20.-21.24.-27
...............23.-25..29.-35.39.-41.45.-51
The left edge is A130668.
I discovered the array 1 1 -2 1 -3 2 in studying the singular points of planar polynomial differential systems (inspired by the reference).
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LINKS
| Paul Curtz, Stabilite locale des systemes quadratiques, Ann. sc. Ecole Norm. Sup. vol 13 no 3 (1980) pp 293-302.
Index to sequences with linear recurrences with constant coefficients, signature (0,1,0,1,0,-1).
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FORMULA
| a(2n)=A004526(n). a(2n+1)=A000027(n+1) .
G.f.: x*(1+x^2+x^3)/((x^2+1)*(x-1)^2*(1+x)^2). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 25 2009]
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CROSSREFS
| Sequence in context: A143862 A115118 A115121 * A189357 A100053 A029194
Adjacent sequences: A124069 A124070 A124071 * A124073 A124074 A124075
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KEYWORD
| nonn,easy
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AUTHOR
| Paul Curtz (bpcrtz(AT)free.fr), Jun 26 2007
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EXTENSIONS
| Partially edited by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 07 2008
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