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A127365 Signed repeated natural numbers. 1
0, 0, -1, -1, 2, 2, -3, -3, 4, 4, -5, -5, 6, 6, -7, -7, 8, 8, -9, -9, 10, 10, -11, -11, 12, 12, -13, -13, 14, 14, -15, -15, 16, 16, -17, -17, 18, 18, -19, -19, 20, 20, -21, -21, 22, 22, -23, -23, 24, 24, -25, -25, 26, 26 (list; graph; refs; listen; history; internal format)
OFFSET

0,5

COMMENTS

Hankel transform of A093387.

FORMULA

G.f.: -x^2*(1+x)/(1+x^2)^2; a(n)=floor(n/2)*(sin(n*pi/2)+cos(n*pi/2)).

CROSSREFS

Sequence in context: A086388 A080513 A111660 * A168050 A065033 A001057

Adjacent sequences:  A127362 A127363 A127364 * A127366 A127367 A127368

KEYWORD

easy,sign

AUTHOR

Paul Barry (pbarry(AT)wit.ie), Jan 11 2007

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Last modified February 14 04:48 EST 2012. Contains 205570 sequences.