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A026763 a(n) = T(2n-1,n-2), T given by A026758. 10
1, 7, 38, 190, 918, 4365, 20594, 96804, 454362, 2132121, 10010203, 47042042, 221337726, 1042837195, 4920447410, 23250646651, 110029743083, 521462857972, 2474929099976, 11762845907633, 55982738983975, 266789302547057 (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 type(n, 'odd') and k <= (n-1)/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) ;

   end if ;

end proc;

seq(T(2*n-1, n-2), n=2..30); # G. C. Greubel, Oct 31 2019

MATHEMATICA

T[n_, k_]:= T[n, k]= If[n<0, 0, If[k==0 || k==n, 1, If[OddQ[n] && 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[2n-1, n-2], {n, 2, 30}] (* G. C. Greubel, Oct 31 2019 *)

PROG

(Sage)

@CachedFunction

def T(n, k):

    if (n<0): return 0

    elif (k==0 or k==n): return 1

    elif (mod(n, 2)==1 and k<=(n-1)/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-2) for n in (2..30)] # G. C. Greubel, Oct 31 2019

CROSSREFS

Cf. A026758, A026759, A026760, A026761, A026762, A026764, A026765, A026766, A026767, A026768.

Sequence in context: A291822 A099453 A292535 * A217340 A037696 A026895

Adjacent sequences:  A026760 A026761 A026762 * A026764 A026765 A026766

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified September 24 17:33 EDT 2021. Contains 347651 sequences. (Running on oeis4.)