OFFSET
1,1
COMMENTS
Twice A195084. - Joerg Arndt, Aug 14 2013
The 1st, 3rd, 5th, 7th, ... "terms" increase by 2, the 2nd, 4th, 6th, 8th, ... decrease by 2. Also the difference between the terms goes up by 2 each time. For example, the difference between 6 and 0 = 6, difference between 0 and 8 = 8, difference between 8 and -2 = 10, and so on.
Also the sequence seems to "mirror" a few terms before the 6, i.e.: -4, 10, -2, 8, 0, 6, 2, 4,[mirror],4, 2, 6, 0, 8, -2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (-1,1,1).
FORMULA
a(n) = 2 * A195084(n). - Joerg Arndt, Aug 14 2013
G.f.: 2*x*(1+4*x+2*x^2)/((1-x)*(1+x)^2). - Joerg Arndt, Aug 14 2013
EXAMPLE
Using the sequence 2+4-6+8-10+12-14-16 gives (2+4)=6, (6-6)=0, (0+8)=8, (8-10)=-2, (-2+12)=10, etc., giving the sequence 6,0,8,-2,10,-4,12,-6,14,-8.
MATHEMATICA
nn = 100; s = 2 Range[2, nn]*Table[(-1)^i, {i, 2, nn}]; s = Join[{2}, s]; Accumulate[s] (* T. D. Noe, Aug 13 2013 *)
CROSSREFS
KEYWORD
sign,less
AUTHOR
D.Wilde, Aug 02 2013
STATUS
approved