A027062 a(n) = A027052(n, 2n-6).

1, 1, 3, 11, 37, 123, 401, 1281, 4023, 12461, 38175, 115939, 349701, 1049063, 3133493, 9327357, 27687947, 82009215, 242473197, 715889685, 2111215763, 6220468653, 18314669783, 53892395679, 158512474561, 466071547105

Offset

3,3

Links

G. C. Greubel, Table of n, a(n) for n = 3..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-6), n=3..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-6], {n, 3, 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-6) for n in (3..30)] # G. C. Greubel, Nov 06 2019

Crossrefs

Sequence in context: A084171 A192875 A118044 * A134757 A094977 A263986

Adjacent sequences: A027059 A027060 A027061 * A027063 A027064 A027065

Keyword

nonn

Author

Clark Kimberling

Status

approved