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A165192
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a(0)=1 a(1)=2 a(3)=3, a(n) = a(n-1)-a(n-3).
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0
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1, 2, 3, 2, 0, -3, -5, -5, -2, 3, 8, 10, 7, -1, -11, -18, -17, -6, 12, 29, 35, 23, -6, -41, -64, -58, -17, 47, 105, 122, 75
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| a(n)=(-1)^n*A104771(n). G.f.: (1+x+x^2)/(1-x+x^3).
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EXAMPLE
| a(3)=2 because 2=3-1 where the 1,3 on the right of the equals sign are the first and third terms of the series.
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PROG
| (Python) series = [1, 2, 3] for i in range(2, 30): .series.append((series[i] - series[i-1])+(series[i-1]-series[i-2])) print series
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CROSSREFS
| Cf. A104771
Sequence in context: A007325 A187038 A056619 * A104771 A056888 A111182
Adjacent sequences: A165189 A165190 A165191 * A165193 A165194 A165195
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KEYWORD
| easy,sign
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AUTHOR
| Ben Thurston (benpaulthurston(AT)gmail.com), Sep 06 2009
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EXTENSIONS
| Offset corrected and recurrence simplified by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 08 2009
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