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A168236
a(n) = (6*n - 3*(-1)^n - 1)/4.
4
2, 2, 5, 5, 8, 8, 11, 11, 14, 14, 17, 17, 20, 20, 23, 23, 26, 26, 29, 29, 32, 32, 35, 35, 38, 38, 41, 41, 44, 44, 47, 47, 50, 50, 53, 53, 56, 56, 59, 59, 62, 62, 65, 65, 68, 68, 71, 71, 74, 74, 77, 77, 80, 80, 83, 83, 86, 86, 89, 89, 92, 92, 95, 95, 98, 98, 101, 101, 104, 104
OFFSET
1,1
COMMENTS
Essentially the same as A168199. - Georg Fischer, Oct 14 2018
FORMULA
G.f.: x*(2 + x^2) / ( (1+x)*(x-1)^2 ).
a(n+1) = A016789(floor(n/2)).
a(n) = a(n-1) +a(n-2) -a(n-3). - Vincenzo Librandi, Sep 16 2013
E.g.f.: (1/4)*(-3 + 4*exp(x) + (6*x - 1)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 16 2016
MATHEMATICA
CoefficientList[Series[(2 + x^2) / ((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 16 2013 *)
Table[(6*n - 3*(-1)^n - 1)/4, {n, 1, 50}] (* or *) LinearRecurrence[ {1, 1, -1}, {2, 2, 5}, 50] (* G. C. Greubel, Jul 16 2016 *)
PROG
(Magma) [3*n/2-1/4-3*(-1)^n/4: n in [1..70]]; // Vincenzo Librandi, Sep 16 2013
CROSSREFS
Cf. A016789.
Sequence in context: A370585 A167177 A145061 * A035624 A340223 A073707
KEYWORD
nonn,easy,less
AUTHOR
Vincenzo Librandi, Nov 21 2009
STATUS
approved