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A216733
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a(1)=1; thereafter a(n) = (n/2)*Sum_{i=1..n-1} K(i,n-i)*a(i)*a(n-i), where K(i,j)=i/j+j/i+2.
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0
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1, 4, 54, 1280, 44500, 2095632, 127881376, 9819500544, 928097190000, 106056995000000, 14432021983025504, 2308065337772034048, 428863163196474895616, 91656939861553564825600, 22332165732277725605760000, 6154560612828089005182025728, 1905106896258617768240402396928, 658221263587332244069472967367680, 252407458471654722567803941053452800
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OFFSET
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1,2
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LINKS
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MAPLE
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K:=(i, j)->i/j+j/i+2;
B:=proc(n) option remember; global K;
if n=1 then 1 else
(n/2)*add( K(i, n-i)*B(i)*B(n-i), i=1..n-1); fi; end;
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MATHEMATICA
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K[i_, j_] := i/j + j/i + 2;
a[1] = 1; a[n_] := a[n] = (n/2) Sum[K[i, n-i] a[i] a[n-i], {i, 1, n-1}];
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CROSSREFS
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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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