cp's OEIS Frontend

A027061 a(n) = A027052(n, 2n-5).

%I A027061 #11 Nov 06 2019 04:27:28
%S A027061 0,2,6,20,66,210,652,1988,5982,17830,52782,155480,456364,1336066,
%T A027061 3904280,11394244,33222902,96812174,282009512,821327088,2391918708,
%U A027061 6966267782,20291422370,59116724728,172271893036,502157965938
%N A027061 a(n) = A027052(n, 2n-5).
%H A027061 G. C. Greubel, <a href="/A027061/b027061.txt">Table of n, a(n) for n = 3..750</a>
%p A027061 T:= proc(n, k) option remember;
%p A027061       if k<0 or k>2*n then 0
%p A027061     elif k=0 or k=2 or k=2*n then 1
%p A027061     elif k=1 then 0
%p A027061     else add(T(n-1, k-j), j=1..3)
%p A027061       fi
%p A027061     end:
%p A027061 seq( T(n,2*n-5), n=3..30); # _G. C. Greubel_, Nov 06 2019
%t A027061 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-5], {n,3,30}] (* _G. C. Greubel_, Nov 06 2019 *)
%o A027061 (Sage)
%o A027061 @CachedFunction
%o A027061 def T(n, k):
%o A027061     if (k<0 or k>2*n): return 0
%o A027061     elif (k==0 or k==2 or k==2*n): return 1
%o A027061     elif (k==1): return 0
%o A027061     else: return sum(T(n-1, k-j) for j in (1..3))
%o A027061 [T(n,2*n-5) for n in (3..30)] # _G. C. Greubel_, Nov 06 2019
%K A027061 nonn
%O A027061 3,2
%A A027061 _Clark Kimberling_