A027064 a(n) = A027052(n, 2n-8).

1, 1, 3, 11, 37, 125, 421, 1405, 4637, 15125, 48777, 155665, 492157, 1543269, 4804663, 14865495, 45745953, 140118817, 427445507, 1299383403, 3937901525, 11902380845, 35891429675, 108009437323, 324455779889, 973119941425

Offset

4,3

Links

G. C. Greubel, Table of n, a(n) for n = 4..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-8), n=4..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-8], {n, 4, 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-8) for n in (4..30)] # G. C. Greubel, Nov 06 2019

Crossrefs

Sequence in context: A094977 A263986 A192339 * A027066 A291415 A046722

Adjacent sequences: A027061 A027062 A027063 * A027065 A027066 A027067

Keyword

nonn

Author

Clark Kimberling

Status

approved