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A140966 - OEIS
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A140966
a(n) = (5 + (-2)^n)/3.
14
2, 1, 3, -1, 7, -9, 23, -41, 87, -169, 343, -681, 1367, -2729, 5463, -10921, 21847, -43689, 87383, -174761, 349527, -699049, 1398103, -2796201, 5592407, -11184809, 22369623, -44739241, 89478487, -178956969, 357913943, -715827881, 1431655767, -2863311529, 5726623063
OFFSET
0,1
COMMENTS
Inverse binomial transform of A048573.
This is an example of the case k=-1 of sequences with recurrences a(n) = k*a(n-1) + (k+3)*a(n-2) - (2*k+2)*a(n-3).
The case k=1 is covered, for example, by A097163, A135520, A136326, A136336, or A137208.
Sequences with k=2 are A094554 and A094555.
Sequences with k=3 are A084175, A108924, and A139818.
FORMULA
a(n) = -a(n-1) + 2*a(n-2).
G.f.: (2+3*x)/((1-x)*(1+2*x)).
a(n+1) - a(n) = (-1)^(n+1)*A000079(n).
a(n+3) = (-1)^n*A083582(n).
a(n+1) - 2*a(n) = -a(n+2).
a(n+1) - 3*a(n) = 5*(-1)^(n+1)*A078008(n) = (-1)^(n+1)*A001045(n-1).
a(2n+3) = -A083584(n), a(2n) = A163834(n). - Philippe Deléham, Feb 24 2014
E.g.f.: (5*exp(x) + exp(-2*x))/3. - Stefano Spezia, Jul 27 2024
MATHEMATICA
(5+(-2)^Range[0, 30])/3 (* or *) LinearRecurrence[{-1, 2}, {2, 1}, 40] (* Harvey P. Dale, Apr 23 2019 *)
PROG
(Magma) [( 5+(-2)^n)/3: n in [0..35]]; // Vincenzo Librandi, Jul 05 2011
(PARI) a(n)=(5+(-2)^n)/3 \\ Charles R Greathouse IV, Oct 07 2015
KEYWORD
sign,easy
AUTHOR
Paul Curtz, Jul 27 2008
EXTENSIONS
Definition simplified by R. J. Mathar, Sep 11 2009
STATUS
approved