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Search: id:A083392
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| 0, -1, 2, -4, 6, -9, 12, -16, 20, -25, 30, -36, 42, -49, 56, -64, 72, -81, 90, -100, 110, -121, 132, -144, 156, -169, 182, -196, 210, -225, 240, -256, 272, -289, 306, -324, 342, -361, 380, -400, 420, -441, 462, -484, 506, -529, 552, -576, 600, -625, 650, -676, 702
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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Sum{i=0, n, (-1)^i*t(i)} where t(i)=i*(i+1)/2
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EXAMPLE
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a(4)=t(0)-t(1)+t(2)-t(3)+t(4)=0-1+3-6+10=6
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PROGRAM
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(PARI) t(n)=n*(n+1)/2 for (n=0, 30, print1(sum(i=0, n, (-1)^i*t(i))", "))
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CROSSREFS
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Cf. A000217, A002620.
Sequence in context: A075354 A086378 A088900 this_sequence A076921 A002620 A087811
Adjacent sequences: A083389 A083390 A083391 this_sequence A083393 A083394 A083395
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KEYWORD
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sign
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AUTHOR
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Jon Perry (perry(AT)globalnet.co.uk), Jun 11 2003
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EXTENSIONS
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More terms from David W. Wilson, Jun 14 2003
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