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A248155
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Expansion of (1 + x - x^2)/((1 + x)*(1 + 2*x)).
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1
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1, -2, 3, -5, 9, -17, 33, -65, 129, -257, 513, -1025, 2049, -4097, 8193, -16385, 32769, -65537, 131073, -262145, 524289, -1048577, 2097153, -4194305, 8388609, -16777217, 33554433, -67108865, 134217729, -268435457, 536870913
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OFFSET
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0,2
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COMMENTS
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Alternating row sums of A105810. Riordan triangle ((1 + x - x^2)/(1 + x)^2, x/(1 + x)).
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LINKS
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FORMULA
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O.g.f.: (1+x-x^2)/((1+x)*(1+2*x)).
a(n) = (3/2)*b(n) + (5/2)*b(n-1), n>=1, a(0) = 1, with b(n) = A225883(n+1).
a(n) = (-1)^n*(1 + 2^(n-1)), n>=1, a(0) = 1.
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PROG
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(PARI) Vec((1 + x - x^2)/((1 + x)*(1 + 2*x)) + O (x^40)) \\ Michel Marcus, Oct 11 2014
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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