cp's OEIS Frontend

A027065 a(n) = A027052(n, 2n-9).

%I A027065 #11 Nov 07 2019 08:28:17
%S A027065 0,2,6,20,68,230,776,2604,8670,28606,93494,302748,971810,3094486,
%T A027065 9782092,30721056,95919714,297938906,921183940,2836545972,8702745304,
%U A027065 26614653494,81159163058,246855070144,749123740876,2268700324802
%N A027065 a(n) = A027052(n, 2n-9).
%H A027065 G. C. Greubel, <a href="/A027065/b027065.txt">Table of n, a(n) for n = 5..750</a>
%p A027065 T:= proc(n, k) option remember;
%p A027065       if k<0 or k>2*n then 0
%p A027065     elif k=0 or k=2 or k=2*n then 1
%p A027065     elif k=1 then 0
%p A027065     else add(T(n-1, k-j), j=1..3)
%p A027065       fi
%p A027065     end:
%p A027065 seq( T(n,2*n-9), n=5..30); # _G. C. Greubel_, Nov 06 2019
%t A027065 T[n_, k_]:= T[n, k]= If[k<0 || k>2*n, 0, If[k==0 || k==2 || k==2*n, 1, If[k==1, 0, Sum[T[n-1, k-j], {j, 3}]]]]; Table[T[n,2*n-9], {n,5,30}] (* _G. C. Greubel_, Nov 06 2019 *)
%o A027065 (Sage)
%o A027065 @CachedFunction
%o A027065 def T(n, k):
%o A027065     if (k<0 or k>2*n): return 0
%o A027065     elif (k==0 or k==2 or k==2*n): return 1
%o A027065     elif (k==1): return 0
%o A027065     else: return sum(T(n-1, k-j) for j in (1..3))
%o A027065 [T(n,2*n-9) for n in (5..30)] # _G. C. Greubel_, Nov 06 2019
%K A027065 nonn
%O A027065 5,2
%A A027065 _Clark Kimberling_