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A026783 a(n) = T(2n, n-2), T given by A026780. 11
1, 11, 84, 557, 3446, 20514, 119336, 684227, 3886460, 21939528, 123347842, 691644044, 3871738018, 21652138770, 121026492186, 676391629701, 3780636102222, 21137831159462, 118234019051048, 661686074145618, 3705252204960252 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 2..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, n-2), n=2..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, n-2], {n, 2, 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, n-2) for n in (2..30)] # G. C. Greubel, Nov 02 2019

CROSSREFS

Cf. A026780, A026781, A026782, A026784, A026785, A026786, A026787, A026788, A026789, A026790.

Sequence in context: A012478 A239461 A330966 * A244975 A271558 A295168

Adjacent sequences:  A026780 A026781 A026782 * A026784 A026785 A026786

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified September 28 19:16 EDT 2021. Contains 347717 sequences. (Running on oeis4.)