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A131259 a(2n)=A000217(n), a(2n+1)=-2*A000217(n). 1
0, 0, 1, -2, 3, -6, 6, -12, 10, -20, 15, -30, 21, -42, 28, -56, 36, -72, 45, -90, 55, -110, 66, -132, 78, -156, 91, -182, 105, -210, 120, -240, 136, -272, 153, -306, 171, -342, 190, -380, 210, -420, 231, -462, 253, -506, 276, -552, 300, -600, 325, -650, 351, -702, 378, -756, 406, -812, 435, -870, 465, -930, 496, -992 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..63.

MAPLE

A000217 := proc(n) n*(n+1)/2 ; end: A131259 := proc(n) if n mod 2 = 0 then A000217(n/2) ; else -2*A000217((n-1)/2) ; fi ; end: seq(A131259(n), n=0..60) ; # R. J. Mathar, Oct 26 2007

CROSSREFS

Cf. A129819.

Sequence in context: A155215 A119319 A069808 * A346758 A143177 A129648

Adjacent sequences:  A131256 A131257 A131258 * A131260 A131261 A131262

KEYWORD

sign,easy

AUTHOR

Paul Curtz, Sep 28 2007

EXTENSIONS

More terms from R. J. Mathar, Oct 26 2007

STATUS

approved

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Last modified October 21 14:18 EDT 2021. Contains 348155 sequences. (Running on oeis4.)