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A334431
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Irregular triangle read by rows: T(m,k) gives the coefficients of x^k of the minimal polynomials of (2*cos(Pi/(2*m)))^2, for m >= 1.
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2
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0, 1, -2, 1, -3, 1, 2, -4, 1, 5, -5, 1, 1, -4, 1, -7, 14, -7, 1, 2, -16, 20, -8, 1, -3, 9, -6, 1, 1, -12, 19, -8, 1, -11, 55, -77, 44, -11, 1, 1, -16, 20, -8, 1
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OFFSET
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1,3
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COMMENTS
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The length of row m is delta(m) + 1 = A055034(m) + 1.
For details see A334429, where the formula for the minimal polynomial MPc2(m, x) of 2*cos(Pi/(2*m))^2 = rho(2*m)^2 is given.
The companion triangle for odd n is A334432.
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LINKS
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FORMULA
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T(m, k) = [x^k] MPc2even(m, x), with MPc2even(m, x) = Product_{j=1..delta(m)} (x - (2 + R(rpnodd(m)_j, rho(m)))) (evaluated using C(m, rho(m)) = 0), for m >= 2, and MPc2even(1, x) = x. Here R(n, x) is the monic Chebyshev R polynomial with coefficients given in A127672. C(n, x) is the minimal polynomial of rho(n) = 2*cos(Pi/n) given in A187360, and rpnodd(m) is the list of positive odd numbers coprime to m and <= m - 1.
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EXAMPLE
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The irregular triangle T(m, k) begins:
m, n \ k 0 1 2 3 4 5 6 ...
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1, 2: 0 1
2, 4: -2 1
3, 6: -3 1
4, 8: 2 -4 1
5, 10: 5 -5 1
6, 12: 1 -4 1
7, 14: -7 14 -7 1
8, 16: 2 -16 20 -8 1
9, 18: -3 9 -6 1
10, 20: 1 -12 19 -8 1
11, 22: -11 55 -77 44 -11 1
12, 24: 1 -16 20 -8 1
13, 26: 13 -91 182 -156 65 -13 1
14, 28: 1 -24 86 -104 53 -12 1
15, 30: 1 -8 14 -7 1
...
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CROSSREFS
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KEYWORD
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sign,tabf,easy
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AUTHOR
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STATUS
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approved
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