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A026784 a(n) = T(2n-1, n-1), T given by A026780. 11
1, 5, 24, 117, 580, 2916, 14834, 76221, 395048, 2063104, 10847078, 57373672, 305110106, 1630489090, 8751851866, 47166202181, 255128842340, 1384688987728, 7538592535170, 41159292861980, 225315261459390, 1236441650047554 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..500

MAPLE

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

    if n<0 then 0;

    elif k=0 or k =n then 1;

    elif k <= n/2 then

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

    else

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

    fi ;

end proc:

seq(T(2*n-1, n-1), n=1..30); # G. C. Greubel, Nov 02 2019

MATHEMATICA

T[n_, k_]:= T[n, k]= If[n<0, 0, If[k==0 || k==n, 1, If[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[2*n-1, n-1], {n, 30}] (* G. C. Greubel, Nov 02 2019 *)

PROG

(Sage)

@CachedFunction

def T(n, k):

    if (n<0): return 0

    elif (k==0 or k==n): return 1

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

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

[T(2*n-1, n-1) for n in (1..30)] # G. C. Greubel, Nov 02 2019

CROSSREFS

Cf. A026780, A026781, A026782, A026783, A026785, A026786, A026787, A026788, A026789, A026790.

Sequence in context: A026707 A235115 A110190 * A017977 A017978 A291245

Adjacent sequences:  A026781 A026782 A026783 * A026785 A026786 A026787

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified May 12 16:02 EDT 2021. Contains 343825 sequences. (Running on oeis4.)