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A154570
The main diagonal of the successive differences of A154127.
4
1, 3, -4, 2, -6, -2, -14, -18, -46, -82, -174, -338, -686, -1362, -2734, -5458, -10926, -21842, -43694, -87378, -174766, -349522, -699054, -1398098, -2796206, -5592402, -11184814, -22369618, -44739246, -89478482, -178956974, -357913938, -715827886
OFFSET
0,2
FORMULA
a(n) = a(n-1) + 2*a(n-2), n>0.
a(n+2) = 2*(-1)^(n+1)*A140966(n).
a(n+5) = -2*A083582(n).
a(2n+1) = 3 - A078008(2n) = 3 - A047849(n).
a(2n+2) = -4 - A078008(2n+1) = -4 - A020988(n).
G.f.: (1+2*x-9*x^2)/((1+x)*(1-2*x)). - R. J. Mathar, Feb 25 2009
MATHEMATICA
f[n_]:=2/(n+1); x=6; Table[x=f[x]; Numerator[x], {n, 0, 5!}](*Absolute Values*) (* Vladimir Joseph Stephan Orlovsky, Mar 12 2010 *)
CROSSREFS
Sequence in context: A179297 A133620 A322965 * A145961 A369557 A375486
KEYWORD
sign
AUTHOR
Paul Curtz, Jan 12 2009
EXTENSIONS
Edited and extended by R. J. Mathar, Feb 25 2009
STATUS
approved