A026527 a(n) = T(2*n, n-2), where T is given by A026519.

1, 3, 14, 55, 231, 952, 3976, 16614, 69750, 293557, 1238952, 5240599, 22212645, 94318875, 401143304, 1708558480, 7286677479, 31113264579, 132994055090, 569048532612, 2437033824302, 10445705817063, 44807461337160, 192342179361800, 826205908069555, 3551172735996756, 15272395383833658

Offset

2,2

Links

G. C. Greubel, Table of n, a(n) for n = 2..1000

Formula

a(n) = A026519(2*n, n-2).

a(n) = A026536(2*n, 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+1)/2], If[EvenQ[n], T[n-1, k-2] + T[n-1, k], T[n-1, k-1] + T[n-1, k-2] + T[n-1, k]]]]; (* T = A026519 *)
a[n_]:= a[n]= Block[{$RecursionLimit = Infinity}, T[2*n, n-2] ];
Table[a[n], {n, 2, 40}] (* G. C. Greubel, Dec 20 2021 *)

Prog

(Sage)
@CachedFunction
def T(n, k): # T = A026552
    if (k==0 or k==2*n): return 1
    elif (k==1 or k==2*n-1): return (n+1)//2
    elif (n%2==0): return T(n-1, k) + T(n-1, k-2)
    else: return T(n-1, k) + T(n-1, k-1) + T(n-1, k-2)
[T(2*n, n-2) for n in (2..40)] # G. C. Greubel, Dec 20 2021

Crossrefs

Cf. A026519, A026520, A026521, A026522, A026523, A026524, A026525, A026526, A026528, AA026529, A026530, A026531, A026533, A026534, A027262, A027263, A027264, A027265, A027266.

Cf. A026536.

Sequence in context: A363964 A322938 A026544 * A037786 A037667 A111468

Adjacent sequences: A026524 A026525 A026526 * A026528 A026529 A026530

Keyword

nonn

Author

Clark Kimberling

Extensions

Terms a(20) onward added by G. C. Greubel, Dec 20 2021

Status

approved