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Expansion of (1-3*x)/(1-7*x).
2

%I #19 Dec 21 2019 15:51:41

%S 1,4,28,196,1372,9604,67228,470596,3294172,23059204,161414428,

%T 1129900996,7909306972,55365148804,387556041628,2712892291396,

%U 18990246039772,132931722278404,930522055948828,6513654391641796,45595580741492572,319169065190448004

%N Expansion of (1-3*x)/(1-7*x).

%C After 1, is this A208704?

%H Colin Barker, <a href="/A270471/b270471.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (7).

%F G.f.: (1-3*x)/(1-7*x).

%F a(n) = 7*a(n-1) for n>1.

%F a(n) = 4*7^(n-1) for n>0.

%t CoefficientList[Series[(1 - 3 x)/(1 - 7 x), {x, 0, 21}], x] (* _Michael De Vlieger_, Mar 18 2016 *)

%t Join[{1},NestList[7#&,4,20]] (* _Harvey P. Dale_, Dec 21 2019 *)

%o (PARI) Vec((1-3*x)/(1-7*x) + O(x^30))

%Y Cf. A208704.

%Y Cf. A000420 (powers of 7), A083076 (partial sums).

%Y Cf. A193577: (1-2*x)/(1-7*x); A169634: (1-4*x)/(1-7*x).

%K nonn,easy

%O 0,2

%A _Colin Barker_, Mar 17 2016