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%I #5 Apr 11 2020 16:23:33
%S 0,2,8,56,624,9536,184480,4313088,118183744,3712870400,131536027008,
%T 5187183672320,225342288987904,10691937463283712,550121848577067520,
%U 30507449271343837184,1813943300823318205440,115116132876009362358272
%N a(n) = 4*(n-1)*a(n-1) -2*(n-1)*a(n-2), with a(0)=0, a(1)=2.
%C This is also the negative of the (1,2) element of the product matrix after multiplying the unit matrix from the
%C left by the matrices (0,-2;j-1,4j-4) in the order j=2 to n.
%t M[n_] := {{0, -2}, {(n - 1), 4*(n - 1)}} v[1] = {0, 1} v[n_] := v[n] = M[n].v[n - 1] a = Table[Abs[v[n][[1]]], {n, 1, 25}]
%t RecurrenceTable[{a[0]==0,a[1]==2,a[n]==4(n-1)a[n-1]-2(n-1)a[n-2]},a,{n,20}] (* _Harvey P. Dale_, Apr 11 2020 *)
%Y Cf. A000166.
%K nonn,easy
%O 0,2
%A _Roger L. Bagula_, Jun 15 2005
%E Definition replaced by recurrence by the Associate Editors of the OEIS, Sep 28 2009
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