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A168376
a(n) = (14*n - 7*(-1)^n - 9)/4.
2
3, 3, 10, 10, 17, 17, 24, 24, 31, 31, 38, 38, 45, 45, 52, 52, 59, 59, 66, 66, 73, 73, 80, 80, 87, 87, 94, 94, 101, 101, 108, 108, 115, 115, 122, 122, 129, 129, 136, 136, 143, 143, 150, 150, 157, 157, 164, 164, 171, 171, 178, 178, 185, 185, 192, 192, 199, 199, 206
OFFSET
1,1
FORMULA
a(n) = 7*n - a(n-1) - 8, with n>1, a(1)=3.
a(n) = A168331(n-1), n>1. - R. J. Mathar, Nov 25 2009
G.f.: x*(3 + 4*x^2)/((1+x) * (x-1)^2). - R. J. Mathar, Nov 25 2009
a(n) = 3 + 7*floor((n-1)/2). - Bruno Berselli, Sep 18 2013
From G. C. Greubel, Jul 19 2016: (Start)
E.g.f.: (1/4)*(-7 + 16*exp(x) + (14*x - 9)*exp(2*x))*exp(-x).
a(n) = a(n-1) + a(n-2) - a(n-3). (End)
MATHEMATICA
Table[7 n/2 - (7 (-1)^n + 9)/4, {n, 60}] (* Bruno Berselli, Sep 17 2013 *)
CoefficientList[Series[(3 + 4 x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 17 2013 *)
PROG
(Magma) [n eq 1 select 3 else 7*n-Self(n-1)-8: n in [1..70]]; // Vincenzo Librandi, Sep 17 2013
(PARI) a(n)=(14*n-7*(-1)^n-9)/4 \\ Charles R Greathouse IV, Jul 19 2016
CROSSREFS
Cf. A168331.
Sequence in context: A057210 A330632 A278832 * A266221 A073709 A085288
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 24 2009
EXTENSIONS
Definition rewritten using Mathar's formula by Bruno Berselli, Sep 17 2013
STATUS
approved