OFFSET
4,2
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-7), 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-7], {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-7) for n in (4..30)] # G. C. Greubel, Nov 06 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved