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Search: id:A135220
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| A135220 |
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Matrices C_n (read by rows), defined by the following identity: C_n * P(X,Y) = P(X+Y, X-Y), where P is any homogenous polynomial of degree n in two variables, represented as a column whose i-th element is the coefficient of X^(n-i)Y^i. |
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+0
1
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| 1, 1, 1, 1, -1, 1, 1, 1, 2, 0, -2, 1, -1, 1, 1, 1, 1, 1, 3, 1, -1, -3, 3, -1, -1, 3, 1, -1, 1, -1, 1, 1, 1, 1, 1, 4, 2, 0, -2, -4, 6, 0, -2, 0, 6, 4, -2, 0, 2, -4, 1, -1, 1, -1, 1, 1, 1, 1, 1, 1, 1, 5, 3, 1, -1, -3, -5, 10, 2, -2, -2, 2, 10, 10, -2, -2, 2, 2, -10, 5, -3, 1, 1, -3, 5, 1, -1, 1, -1, 1, -1
(list; graph; listen)
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OFFSET
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1,9
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FORMULA
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Formula: (C_n)ij = Sum(k=0..j, (-1)^k * C(j, k) * C(n-j, i-k)).
Recurrence: (C_n)i,j = (C_(n-1))i,j + (C_(n-1))i-1,j for all j < n; (C_n)i,j = (C_(n-1))i,j-1 - (C_(n-1))i-1,j-1 for all j > 0.
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EXAMPLE
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C_0 = [1]
C_1 = [1 1 / 1 -1]
C_2 is equal to:
|1 1 1|
|2 0 -2|
|1 -1 1|
since if
P(X,Y) = a0*X^2 + a1*XY + a2*Y^2
then
P(X+Y,X-Y) = (a0 + a1 + a2)*X^2 + (2*a0 - 2*a2)*XY + (a0 - a1 + a2)*Y^2
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CROSSREFS
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Sequence in context: A026610 A094451 A056562 this_sequence A068320 A111330 A117447
Adjacent sequences: A135217 A135218 A135219 this_sequence A135221 A135222 A135223
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KEYWORD
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easy,tabf,sign
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AUTHOR
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Ilia Smilga (ilia.smilga(AT)orange.fr), Feb 14 2008, Feb 20 2008
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