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Search: id:A089594
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| A089594 |
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Alternating sum of squares to n. |
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+0
1
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| -1, 3, -6, 10, -15, 21, -28, 36, -45, 55, -66, 78, -91, 105, -120, 136, -153, 171, -190, 210, -231, 253, -276, 300, -325, 351, -378, 406, -435, 465, -496, 528, -561, 595, -630, 666, -703, 741, -780, 820, -861, 903, -946, 990, -1035, 1081, -1128, 1176, -1225, 1275
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(n)=sum{i=1, n, (-1)^n*n^2}
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EXAMPLE
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a(6)=-1*1+1*4-1*9+1*16-1*25+1*36=-1+4-9+16-25+36=3+7+11=21
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MAPLE
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seq(sum(binomial(n, m), m=1..2)-n^2, n=2..51); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 19 2008
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PROGRAM
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(PARI) for(i=1, 50, print1(", "sum(j=1, i, (-1)^j*j^2)))
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CROSSREFS
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Cf. A000217.
Sequence in context: A105337 A105338 A105339 this_sequence A000217 A105340 A109811
Adjacent sequences: A089591 A089592 A089593 this_sequence A089595 A089596 A089597
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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), Dec 30 2003
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