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A152815
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Triangle T(n,k), read by rows given by [1,0,-1,0,0,0,0,0,0,...] DELTA [0,1,-1,0,0,0,0,0,0,...] where DELTA is the operator defined in A084938.
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15
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1, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 2, 1, 0, 0, 1, 2, 1, 0, 0, 0, 1, 3, 3, 1, 0, 0, 0, 1, 3, 3, 1, 0, 0, 0, 0, 1, 4, 6, 4, 1, 0, 0, 0, 0, 1, 4, 6, 4, 1, 0, 0, 0, 0, 0, 1, 5, 10, 10, 5, 1, 0, 0, 0, 0, 0, 1, 5, 10, 10, 5, 1, 0, 0, 0, 0, 0, 0, 1, 6, 15, 20, 15, 6, 1, 0, 0, 0, 0, 0, 0, 1, 6, 15, 20, 15, 6, 1, 0, 0, 0
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,12
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COMMENTS
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Triangle read by rows, Pascal's triangle (A007318) rows repeated.
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LINKS
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FORMULA
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T(n,k) = T(n-1,k) + ((1+(-1)^n)/2)*T(n-1,k-1).
G.f.: (1+x)/(1-(1+y)*x^2).
Sum_{k=0..n} T(n,k)*x^k = A000012(n), A016116(n), A108411(n), A213173(n), A074872(n+1) for x = 0,1,2,3,4 respectively. - Philippe Deléham, Nov 26 2011, Apr 22 2013
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EXAMPLE
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Triangle begins:
1;
1, 0;
1, 1, 0;
1, 1, 0, 0;
1, 2, 1, 0, 0;
1, 2, 1, 0, 0, 0;
1, 3, 3, 1, 0, 0, 0;
1, 3, 3, 1, 0, 0, 0, 0;
1, 4, 6, 4, 1, 0, 0, 0, 0; ...
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MATHEMATICA
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m = 13;
DELTA[Join[{1, 0, -1}, Table[0, {m}]], Join[{0, 1, -1}, Table[0, {m}]], m] // Flatten (* Jean-François Alcover, Feb 19 2020 *)
T[n_, k_] := If[n<0, 0, Binomial[Floor[n/2], k]]; (* Michael Somos, Oct 01 2022 *)
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PROG
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(Haskell)
a152815 n k = a152815_tabl !! n !! k
a152815_row n = a152815_tabl !! n
a152815_tabl = [1] : [1, 0] : t [1, 0] where
t ys = zs : zs' : t zs' where
zs' = zs ++ [0]; zs = zipWith (+) ([0] ++ ys) (ys ++ [0])
{T(n, k) = if(n<0, 0, binomial(n\2, k))}; /* Michael Somos, Oct 01 2022 */
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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