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A026590 a(n) = T(2*n, n), where T is given by A026584. 17
1, 1, 5, 19, 69, 341, 1203, 6336, 22593, 121483, 438533, 2381512, 8677763, 47419503, 173984792, 954961034, 3522101709, 19397198595, 71831252031, 396646918211, 1473610012405, 8154682794333, 30376120747792, 168394714422722, 628648474795879, 3490216221862041, 13053833414221023, 72566287730964469 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
LINKS
FORMULA
a(n) = A026584(n, n).
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]];
Table[a[n], {n, 0, 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) for n in (0..40)] # G. C. Greubel, Dec 13 2021
CROSSREFS
Sequence in context: A055991 A030662 A149758 * A243413 A222538 A095073
KEYWORD
nonn
AUTHOR
EXTENSIONS
Terms a(19) onward from G. C. Greubel, Dec 13 2021
STATUS
approved

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Last modified March 29 08:53 EDT 2024. Contains 371268 sequences. (Running on oeis4.)