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A027030 a(n) = T(n,2n-6), T given by A027023.

%I A027030 #8 Nov 05 2019 07:23:24
%S A027030 1,1,5,17,57,189,613,1949,6097,18825,57525,174353,525049,1573077,
%T A027030 4693909,13960805,41415089,122603341,362343053,1069436317,3152995209,
%U A027030 9287942097,27341397469,80443393889,236581555233,695561538977
%N A027030 a(n) = T(n,2n-6), T given by A027023.
%H A027030 G. C. Greubel, <a href="/A027030/b027030.txt">Table of n, a(n) for n = 3..750</a>
%p A027030 T:= proc(n, k) option remember;
%p A027030       if k<3 or k=2*n then 1
%p A027030     else add(T(n-1, k-j), j=1..3)
%p A027030       fi
%p A027030     end:
%p A027030 seq(T(n,2*n-6), n=3..30); # _G. C. Greubel_, Nov 05 2019
%t A027030 T[n_, k_]:= T[n, k]= If[n<0, 0, If[k<3 || k==2*n, 1, Sum[T[n-1, k-j], {j, 3}]]]; Table[T[n, 2*n-6], {n,3,30}] (* _G. C. Greubel_, Nov 05 2019 *)
%o A027030 (Sage)
%o A027030 @CachedFunction
%o A027030 def T(n, k):
%o A027030     if (k<3 or k==2*n): return 1
%o A027030     else: return sum(T(n-1, k-j) for j in (1..3))
%o A027030 [T(n, 2*n-6) for n in (3..30)] # _G. C. Greubel_, Nov 04 2019
%K A027030 nonn
%O A027030 3,3
%A A027030 _Clark Kimberling_