A027060 a(n) = T(n,2n-4), T given by A027052.

1, 1, 3, 11, 35, 107, 319, 935, 2713, 7825, 22491, 64523, 184945, 530001, 1519151, 4356471, 12501301, 35901325, 103188123, 296844379, 854701935, 2463133311, 7104685935, 20510632575, 59262772629, 171373598341, 495968905267

Offset

2,3

Links

G. C. Greubel, Table of n, a(n) for n = 2..750

Maple

T:= proc(n, k) option remember;
      if k<0 or k>2*n then 0
    elif k=0 or k=2 or k=2*n then 1
    elif k=1 then 0
    else add(T(n-1, k-j), j=1..3)
      fi
    end:
seq( T(n, 2*n-4), n=2..30); # G. C. Greubel, Nov 06 2019

Mathematica

T[n_, k_]:= T[n, k]= If[k<0 || k>2*n, 0, If[k==0 || k==2 || k==2*n, 1, If[k==1, 0, Sum[T[n-1, k-j], {j, 3}]]]]; Table[T[n, 2*n-4], {n, 2, 30}] (* G. C. Greubel, Nov 06 2019 *)

Prog

(Sage)
@CachedFunction
def T(n, k):
    if (k<0 or k>2*n): return 0
    elif (k==0 or k==2 or k==2*n): return 1
    elif (k==1): return 0
    else: return sum(T(n-1, k-j) for j in (1..3))
[T(n, 2*n-4) for n in (2..30)] # G. C. Greubel, Nov 06 2019

Crossrefs

Sequence in context: A223626 A088578 A320683 * A171498 A126939 A370199

Adjacent sequences: A027057 A027058 A027059 * A027061 A027062 A027063

Keyword

nonn

Author

Clark Kimberling

Status

approved