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A172018
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a(n) = A142458(2*n-1, n)/n.
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1
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1, 4, 182, 27410, 8890310, 5051270688, 4459786293372, 5659222645997646, 9770821427711370950, 22041005972637205198568, 62967534725721252354766676, 222256499446324679350316816644, 950020052553444052606973276792092, 4836606673194788521307702032786510240, 28920975283745982162014025622769293094712
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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LINKS
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FORMULA
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MATHEMATICA
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T[n_, k_, m_]:= T[n, k, m]= If[k==1 || k==n, 1, (m*n-m*k+1)*T[n-1, k-1, m] + (m*k-m+1)*T[n-1, k, m]];
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PROG
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(Sage)
@CachedFunction
def T(n, k, m):
if (k==1 or k==n): return 1
else: return (m*(n-k)+1)*T(n-1, k-1, m) + (m*k-m+1)*T(n-1, k, m)
def A172018(n): return T(2*n-1, n, 3)/n
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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Offset changed and more terms added by G. C. Greubel, Mar 16 2022
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STATUS
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approved
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