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A164111
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Expansion of (1-x)/(1+4x^2).
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2
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1, -1, -4, 4, 16, -16, -64, 64, 256, -256, -1024, 1024, 4096, -4096, -16384, 16384, 65536, -65536, -262144, 262144, 1048576, -1048576, -4194304, 4194304, 16777216, -16777216, -67108864, 67108864, 268435456, -268435456, -1073741824
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| Hankel transform of 1,1,0,2,0,6,0,70,... (which has g.f. 1+x/sqrt(1-4x^2). See A126869).
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FORMULA
| a(n)=(-1)^C(n+1,2)*(4^(n/2)*(1+(-1)^n)/2+4^((n-1)/2)(1-(-1)^n)/2).
a(n+3) = a(n+2)*a(n+1)/a(n). [Reinhard Zumkeller, Mar 04 2011]
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CROSSREFS
| Sequence in context: A196064 A056450 A141125 * A164906 A170833 A129884
Adjacent sequences: A164108 A164109 A164110 * A164112 A164113 A164114
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KEYWORD
| easy,sign
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Aug 10 2009
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