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A152418 A sevens sequence: a(n)=(7^n - 1)/(2^(4 - 3*Mod[n, 2])). 1

%I

%S 0,3,3,171,150,8403,7353,411771,360300,20176803,17654703,988663371,

%T 865080450,48444505203,42388942053,2373780754971,2077058160600,

%U 116315256993603,101775849869403,5699447592686571,4987016643600750

%N A sevens sequence: a(n)=(7^n - 1)/(2^(4 - 3*Mod[n, 2])).

%H Colin Barker, <a href="/A152418/b152418.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,50,0,-49).

%F a(n) = (7^n - 1)/(2^(4 - 3*Mod[n, 2])).

%F a(n) = 50*a(n-2)-49*a(n-4). - _Colin Barker_, Nov 06 2014

%F G.f.: 3*x*(7*x^2+x+1) / ((x-1)*(x+1)*(7*x-1)*(7*x+1)). - _Colin Barker_, Nov 06 2014

%t a[n_] := (7^n - 1)/(2^(4 - 3*Mod[n, 2]));

%t Table[a[n], {n, 0, 30}]

%o PARI) concat(0, Vec(3*x*(7*x^2+x+1)/((x-1)*(x+1)*(7*x-1)*(7*x+1)) + O(x^100))) \\ _Colin Barker_, Nov 06 2014

%Y Cf. A003462.

%K nonn,easy

%O 0,2

%A _Roger L. Bagula_, Dec 03 2008

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Last modified November 18 17:33 EST 2019. Contains 329287 sequences. (Running on oeis4.)