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A107856 a(n) = 2*a(n-2)+4*a(n-4)+a(n-6), n>9. 0

%I

%S 1,1,1,0,4,4,11,7,37,30,122,92,403,311,1331,1020,4396,3376,14519,

%T 11143,47953,36810,158378,121568,523087,401519,1727639,1326120,

%U 5706004,4379884,18845651,14465767,62242957,47777190,205574522,157797332

%N a(n) = 2*a(n-2)+4*a(n-4)+a(n-6), n>9.

%F Limit_{n->infinity} a(n)/a(n-1) alternates between 0.767592... and 4.3027...

%F G.f.: x*(1+x+x^2)*(2*x^6+2*x^2-1)/( (1+x^2)*(x^4+3*x^2-1)) [Sep 28 2009]

%t M[n_] := If [Mod[n, 2] == 0, {{0, 1, 0, 0}, {0, 0, 1, 0}, {0, 0, 0, 1}, {1, 3, 0, -3}}, {{0, 1, 0, 0}, {0, 0, 1, 0}, {0, 0, 0, 1}, {0, 0, 1, 1}}] v[1] = {1, 1, 1, 0} v[n_] := v[n] = M[n].v[n - 1] a0 = Table[Abs[v[n][[1]]], {n, 1, 50}]

%K nonn,easy

%O 1,5

%A _Roger L. Bagula_, Jun 12 2005

%E Definition replaced by recurrence by the Associate Editors of the OEIS, Sep 28 2009

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Last modified August 14 13:57 EDT 2020. Contains 336481 sequences. (Running on oeis4.)