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A026782
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a(n) = T(2n,n-1), T given by A026780.
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11
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1, 7, 40, 217, 1158, 6150, 32656, 173719, 926664, 4958556, 26619438, 143365880, 774562478, 4197344582, 22810572062, 124300860689, 679081142350, 3718894341450, 20412141531664, 112276061739814, 618806031336236, 3416954495002676
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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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MAPLE
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T:= proc(n, k) option remember;
if n<0 then 0;
elif k=0 or k =n then 1;
elif k <= n/2 then
procname(n-1, k-1)+procname(n-2, k-1)+procname(n-1, k) ;
else
procname(n-1, k-1)+procname(n-1, k) ;
fi ;
end proc:
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MATHEMATICA
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T[n_, k_]:= T[n, k]= If[n<0, 0, If[k==0 || k==n, 1, If[k<=n/2, T[n-1, k-1] + T[n-2, k-1] + T[n-1, k], T[n-1, k-1] + T[n-1, k] ]]];
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PROG
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(Sage)
@CachedFunction
def T(n, k):
if (n<0): return 0
elif (k==0 or k==n): return 1
elif (k<=n/2): return T(n-1, k-1) + T(n-2, k-1) + T(n-1, k)
else: return T(n-1, k-1) + T(n-1, k)
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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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