OFFSET
3,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 3..1000
FORMULA
a(n) = A026536(n, n-3).
MATHEMATICA
T[n_, k_]:= T[n, k]= If[k==0 || k==2*n, 1, If[k==1 || k==2*n-1, Floor[n/2], If[EvenQ[n], T[n-1, k-2] + T[n-1, k-1] + T[n-1, k], T[n-1, k-2] + T[n-1, k]] ]]; Table[T[n, n-3], {n, 3, 40}] (* G. C. Greubel, Apr 10 2022 *)
PROG
(SageMath)
@CachedFunction
def T(n, k): # A026536
if k < 0 or n < 0: return 0
elif k == 0 or k == 2*n: return 1
elif k == 1 or k == 2*n-1: return n//2
elif n % 2 == 1: return T(n-1, k-2) + T(n-1, k)
return T(n-1, k-2) + T(n-1, k-1) + T(n-1, k)
def A026540(n): return T(n, n-3)
[A026540(n) for n in (3..40)] # G. C. Greubel, Apr 10 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved