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A055824
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a(n) = T(2*n,n), array T as in A055818.
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8
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1, 2, 9, 43, 217, 1131, 6017, 32467, 177009, 972691, 5378425, 29889531, 166795977, 934039419, 5246059761, 29540072355, 166708076001, 942651407907, 5339465635049, 30291114653131, 172081678284729, 978807205953931
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OFFSET
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0,2
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LINKS
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MAPLE
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T:= proc(i, j) option remember;
if i=0 or j=0 then 1
else add(add(T(h, m), m=0..j), h=0..i-1)
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MATHEMATICA
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T[i_, j_]:= T[i, j]= If[i==0 || j==0, 1, Sum[T[h, m], {h, 0, i-1}, {m, 0, j}]]; Table[T[n, n], {n, 0, 25}] (* G. C. Greubel, Jan 22 2020 *)
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PROG
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(Sage)
@CachedFunction
def T(i, j):
if (i==0 or j==0): return 1
else: return sum(sum(T(h, m) for m in (0..j)) for h in (0..i-1))
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CROSSREFS
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Cf. A055818, A055819, A055820, A055821, A055822, A055823, A055825, A055826, A055827, A055828, A055829.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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