A026547 a(n) = T(n, floor(n/2)), T given by A026536.

1, 1, 1, 1, 5, 6, 16, 19, 65, 79, 251, 306, 1016, 1247, 4117, 5069, 16913, 20889, 69865, 86479, 290455, 360205, 1212905, 1506462, 5085224, 6324176, 21389824, 26630423, 90226449, 112439094, 381519416, 475838291, 1616684241, 2017827545

Offset

0,5

Links

G. C. Greubel, Table of n, a(n) for n = 0..340

Formula

a(n) = A026536(n, floor(n/2)).

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, Floor[n/2]], {n, 0, 40}] (* G. C. Greubel, Apr 11 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 A026547(n): return T(n, n//2)
[A026547(n) for n in (0..40)] # G. C. Greubel, Apr 11 2022

Crossrefs

Cf. A026536.

Sequence in context: A118712 A130878 A104422 * A081283 A058567 A115376

Adjacent sequences: A026544 A026545 A026546 * A026548 A026549 A026550

Keyword

nonn

Author

Clark Kimberling

Status

approved