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%I #12 Oct 10 2018 12:52:54
%S 0,1,0,0,4,1,0,28,12,1,280,160,24,3641,2520,520,58280,46481,11880,
%T 1107840,987900,295961,24384360,23829540,8090964,609904961,643952400,
%U 242285568,17085429872,19284524561,7912519440
%N a(n) = n*a(n-3) + a(n-4) for n >= 4.
%F a(n) = n*a(n-3) + a(n-4) for n >= 4. - _Jianing Song_, Oct 10 2018
%t M[n_] := {{0, 0, n, 1}, {1, 0, 0, 0}, {0, 1, 0, 0}, {0, 0, 1, 0}};
%t v[0] = {0, 0, 0, 1};
%t v[n_] := v[n] = M[n].v[n - 1];
%t a = Table[v[n][[1]], {n, 0, 30}]
%o (PARI) a(n) = if(n<4, n==1, n*a(n-3) + a(n-4)) \\ _Jianing Song_, Oct 10 2018
%K nonn,easy
%O 0,5
%A _Roger L. Bagula_, Jun 19 2007
%E Edited, new name, and offset corrected by _Jianing Song_, Oct 10 2018
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