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A106192 Expansion of sqrt(1-4x)/(1-x^2). 2
1, -2, -1, -6, -11, -34, -95, -298, -953, -3158, -10677, -36750, -128249, -452774, -1614049, -5801654, -21003739, -76516994, -280293319, -1031794394, -3814819699, -14160035234, -52747353739, -197125162514, -738866581039, -2776933457162, -10462759383943 (list; graph; refs; listen; history; internal format)
OFFSET

0,2

COMMENTS

Diagonal sums of number triangle A106190.

FORMULA

a(n)=sum{k=0..floor(n/2), binomial(2(n-2k), n-2k)/(1-2(n-2k))}.

CROSSREFS

Sequence in context: A039762 A039795 A049949 * A113025 A113216 A081064

Adjacent sequences:  A106189 A106190 A106191 * A106193 A106194 A106195

KEYWORD

easy,sign

AUTHOR

Paul Barry (pbarry(AT)wit.ie), Apr 24 2005

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Last modified February 15 14:20 EST 2012. Contains 205811 sequences.