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A026750 a(n) = T(2n,n-2), T given by A026747.

%I A026750 #9 Oct 29 2019 21:11:03
%S A026750 1,9,58,329,1753,9020,45442,225860,1112543,5446607,26550968,129042976,
%T A026750 625860205,3031021096,14664729519,70906318405,342717456708,
%U A026750 1656208470644,8003645557573,38681730323747,186985728069661,904119336235884
%N A026750 a(n) = T(2n,n-2), T given by A026747.
%H A026750 G. C. Greubel, <a href="/A026750/b026750.txt">Table of n, a(n) for n = 2..500</a>
%p A026750 A026747 := proc(n,k) option remember;
%p A026750    if k=0 or k = n then 1;
%p A026750    elif type(n,'even') and k <= n/2 then
%p A026750         procname(n-1,k-1)+procname(n-2,k-1)+procname(n-1,k) ;
%p A026750    else
%p A026750        procname(n-1,k-1)+procname(n-1,k) ;
%p A026750    end if ;
%p A026750 end proc:
%p A026750 seq(A026747(2*n,n-2), n=2..30); # _G. C. Greubel_, Oct 29 2019
%t A026750 T[n_, k_]:= T[n, k]= If[k==0 || k==n, 1, If[EvenQ[n] && k<=n/2, T[n-1, k -1] + T[n-2, k-1] + T[n-1, k], T[n-1, k-1] + T[n-1, k] ]]; Table[T[2n, n-2], {n,2,30}] (* _G. C. Greubel_, Oct 29 2019 *)
%o A026750 (Sage)
%o A026750 @CachedFunction
%o A026750 def T(n, k):
%o A026750     if (k==0 or k==n): return 1
%o A026750     elif (mod(n,2)==0 and k<=n/2): return T(n-1,k-1) + T(n-2,k-1) + T(n-1,k)
%o A026750     else: return T(n-1,k-1) + T(n-1,k)
%o A026750 [T(2*n, n-2) for n in (2..30)] # _G. C. Greubel_, Oct 29 2019
%Y A026750 Cf. A026747, A026748, A026749, A026751, A026752, A026753, A026754, A026755, A026756, A026757.
%K A026750 nonn
%O A026750 2,2
%A A026750 _Clark Kimberling_