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A117423 Column 5 of triangle A117418. 7
1, 6, 28, 126, 572, 2692, 13203, 67542, 360117, 1999817, 11541894, 69098409, 428183782, 2742315847, 18117294723, 123222721469, 861339730328, 6179291890400, 45431581077388, 341893183760356, 2630537501336631 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
FORMULA
a(n) = A117418(n+5, 5). - G. C. Greubel, May 31 2021
MATHEMATICA
A117418[n_, k_]:= A117418[n, k]= If[k<0 || k>n, 0, If[k==0 || k==n, 1, If[k==n-1, n, Sum[A117418[n -Floor[(k+1)/2], Floor[k/2] +j]*A117418[Floor[(k-1)/2] +j, Floor[(k-1)/2]], {j, 0, n-k}] ]]];
Table[A117418[n+5, 5], {n, 0, 30}] (* G. C. Greubel, May 31 2021 *)
PROG
(Sage)
@CachedFunction
def A117418(n, k):
if (k==0 or k==n): return 1
elif (k==n-1): return n
else: return sum( A117418(n -(k+1)//2, k//2 +j)*A117418((k-1)//2 +j, (k-1)//2) for j in (0..n-k))
[A117418(n+5, 5) for n in (0..30)] # G. C. Greubel, May 31 2021
CROSSREFS
Sequence in context: A181337 A002693 A289779 * A351053 A171859 A338584
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Mar 14 2006
STATUS
approved

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Last modified March 4 12:21 EST 2024. Contains 370532 sequences. (Running on oeis4.)