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A026774 a(n) = T(2n-1,n-2), T given by A026769. 11

%I

%S 1,8,49,276,1504,8082,43193,230536,1231484,6591350,35369380,190329098,

%T 1027180798,5559635866,30176648513,164237973028,896188159820,

%U 4902187071922,26877397858264,147684225578318,813159429830590

%N a(n) = T(2n-1,n-2), T given by A026769.

%H G. C. Greubel, <a href="/A026774/b026774.txt">Table of n, a(n) for n = 2..500</a>

%p T:= proc(n,k) option remember;

%p if n<0 then 0;

%p elif k=0 or k=n then 1;

%p elif n=2 and k=1 then 2;

%p elif k <= (n-1)/2 then

%p procname(n-1,k-1)+procname(n-2,k-1)+procname(n-1,k) ;

%p else

%p procname(n-1,k-1)+procname(n-1,k) ;

%p end if ;

%p end proc;

%p seq(T(2*n-1, n-2), n=2..30); # _G. C. Greubel_, Nov 01 2019

%t T[n_, k_]:= T[n, k]= If[n<0, 0, If[k==0 || k==n, 1, If[n==2 && k==1, 2, If[k<=(n-1)/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[2*n-1, n-2], {n,2,30}] (* _G. C. Greubel_, Nov 01 2019 *)

%o (Sage)

%o @CachedFunction

%o def T(n, k):

%o if (k==0 or k==n): return 1

%o elif (n==2 and k==1): return 2

%o elif (k<=(n-1)/2): return T(n-1,k-1) + T(n-2,k-1) + T(n-1,k)

%o else: return T(n-1,k-1) + T(n-1,k)

%o [T(2*n-1, n-2) for n in (2..30)] # _G. C. Greubel_, Nov 01 2019

%Y Cf. A026769, A026770, A026771, A026772, A026773, A026775, A026776, A026777, A026778, A026779.

%K nonn

%O 2,2

%A _Clark Kimberling_

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Last modified November 22 08:46 EST 2019. Contains 329389 sequences. (Running on oeis4.)