A026592 a(n) = T(2*n, n-2), where T is given by A026584.

1, 3, 14, 65, 251, 1288, 4830, 25518, 95388, 510532, 1910821, 10309234, 38656462, 209766714, 787912030, 4294635438, 16155375825, 88371236851, 332859949946, 1826080683788, 6885797551334, 37867515477338, 142929375411104, 787637258527505, 2975423924172735, 16425495119248041, 62096233990615140, 343318987947145114

Offset

2,2

Links

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

Formula

a(n) = A026584(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/2], If[EvenQ[n+k], T[n-1, k-2] + T[n-1, k], T[n-1, k-2] + T[n-1, k-1] + T[n-1, k] ]]]; (* T = A026584 *)
a[n_]:= a[n]= Block[{$RecursionLimit= Infinity}, T[2*n, n-2]];
Table[a[n], {n, 2, 40}] (* G. C. Greubel, Dec 13 2021 *)

Prog

(Sage)
@CachedFunction
def T(n, k):  # T = A026584
    if (k==0 or k==2*n): return 1
    elif (k==1 or k==2*n-1): return (n//2)
    else: return T(n-1, k-2) + T(n-1, k) if ((n+k)%2==0) else T(n-1, k-2) + T(n-1, k-1) + T(n-1, k)
[T(2*n, n-2) for n in (2..40)] # G. C. Greubel, Dec 13 2021

Crossrefs

Cf. A026584, A026585, A026587, A026589, A026590, A026591, A026593, A026594, A026595, A026596, A026597, A026598, A026599, A027282, A027283, A027284, A027285, A027286.

Sequence in context: A151240 A161131 A247978 * A034275 A240008 A151322

Adjacent sequences: A026589 A026590 A026591 * A026593 A026594 A026595

Keyword

nonn

Author

Clark Kimberling

Extensions

Terms a(19) onward added by G. C. Greubel, Dec 13 2021

Status

approved