OFFSET
1,1
COMMENTS
LINKS
FORMULA
a(n) = (-5*(-1)^n + 1)/2.
a(n+1) - a(n) = 5*(-1)^n.
a(n) = -a(n-1) + 1 for n > 1; a(1) = 3.
a(n) = a(n-2) for n > 2; a(1) = 3, a(2) = -2.
G.f.: x*(3 - 2*x)/((1-x)*(1+x)).
a(n) = A049071(n). - R. J. Mathar, Nov 25 2009
E.g.f.: (1/2)*(1 - exp(-x))*(5 + exp(x)). - G. C. Greubel, Jul 18 2016
MATHEMATICA
LinearRecurrence[{0, 1}, {3, -2}, 25] (* G. C. Greubel, Jul 18 2016 *)
PadRight[{}, 120, {3, -2}] (* Harvey P. Dale, Oct 05 2016 *)
PROG
(Magma) &cat[[3, -2]: n in [1..42]];
(Magma) [n eq 1 select 3 else -Self(n-1)+1:n in [1..84]];
(Magma) [(-5*(-1)^n+1)/2: n in [1..100]]; // Vincenzo Librandi, Jul 19 2016
(PARI) a(n)=3-n%2*5 \\ Charles R Greathouse IV, Jul 13 2016
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Klaus Brockhaus, Nov 23 2009
STATUS
approved