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Search: id:A118401
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| A118401 |
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Triangle, read by rows, equal to the matrix square of triangle A118400; also equals the matrix inverse of triangle A118407. |
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+0
5
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| 1, 0, 1, 2, 0, 1, -2, 2, 0, 1, 4, -2, 2, 0, 1, -6, 4, -2, 2, 0, 1, 8, -6, 4, -2, 2, 0, 1, -10, 8, -6, 4, -2, 2, 0, 1, 12, -10, 8, -6, 4, -2, 2, 0, 1, -14, 12, -10, 8, -6, 4, -2, 2, 0, 1, 16, -14, 12, -10, 8, -6, 4, -2, 2, 0, 1, -18, 16, -14, 12, -10, 8, -6, 4, -2, 2, 0, 1, 20, -18, 16, -14, 12, -10, 8, -6, 4, -2, 2, 0, 1
(list; table; graph; listen)
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OFFSET
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0,4
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COMMENT
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This triangle has an integer matrix square-root (A118400) if the main diagonal of the square-root is allowed to be signed. Even though the columns of this triangle are all the same, the columns of the matrix square-root A118400 are all different.
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FORMULA
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G.f.: A(x,y) = (1 + 2*x + 2*x^2)*(1+x^2)/(1+x)^2/(1-x*y). Column g.f.: (1 + 2*x + 2*x^2)*(1+x^2)/(1+x)^2.
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EXAMPLE
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Triangle begins:
1;
0, 1;
2, 0, 1;
-2, 2, 0, 1;
4,-2, 2, 0, 1;
-6, 4,-2, 2, 0, 1;
8,-6, 4,-2, 2, 0, 1;
-10, 8,-6, 4,-2, 2, 0, 1;
12,-10, 8,-6, 4,-2, 2, 0, 1;
-14, 12,-10, 8,-6, 4,-2, 2, 0, 1;
16,-14, 12,-10, 8,-6, 4,-2, 2, 0, 1; ...
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PROGRAM
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(PARI) {T(n, k)=polcoeff(polcoeff((1+2*x+2*x^2)*(1+x^2)/(1+x)^2/(1-x*y+x*O(x^n)), n, x)+y*O(y^k), k, y)}
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CROSSREFS
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Cf. A118400 (matrix square-root), A118402 (row sums), A118403 (unsigned row sums), A118407 (matrix inverse).
Adjacent sequences: A118398 A118399 A118400 this_sequence A118402 A118403 A118404
Sequence in context: A091602 A035465 A096144 this_sequence A113678 A110249 A067460
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KEYWORD
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sign,tabl
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com), Apr 27 2006
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