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A117422 Column 4 of triangle A117418. 7
1, 5, 20, 79, 322, 1385, 6293, 30152, 151842, 801220, 4414013, 25314411, 150707813, 929456660, 5924776551, 38954031366, 263667692262, 1834336985083, 13095675086752, 95805809484401, 717326794547940, 5490635404488630 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
FORMULA
a(n) = A117418(n+4, 4). - 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+4, 4], {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+4, 4) for n in (0..30)] # G. C. Greubel, May 31 2021
CROSSREFS
Sequence in context: A346394 A079820 A275907 * A154639 A214939 A162925
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Mar 14 2006
STATUS
approved

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Last modified February 21 12:17 EST 2024. Contains 370235 sequences. (Running on oeis4.)