OFFSET
1,3
COMMENTS
The length of row n of this irregular triangle t(n, k) is 2^(n-1) = A000079(n-1), n >= 1.
These polynomials P(n, y^2) = Sum_{k=0..2^(n-1)-1} t(n, k)*y^2 appear in table 2 (Tabelle 2), p. 157, of Carl Schick's book as x_n/(2^n*x*y), for n >= 1, and x_0 = x. The polynomials y_n of Tabelle 1 on p. 156 appear as y_n = -Sum_{n=0..2^(n-1)} A321369(n, k)*y^(2*k), for n >= 1, with y_0 = y, and are related to the n-th iteration of the Chebyshev polynomial -T(2, y) = 1 - 2*x^2.
Originally the polynomials y_n and x_n are defined in Schick's rare notebook as: y_n = 1 - 2*(y_{n-1})^2, for n >= 1, with y_0 = y, and x_n/(2^n*x*y) = Product_{j=1..n-1} y_j, for n >= 1, and x_0 = x. The (x_n, y_n) come from coordinates of points on the unit circle with x_n = cos(phi_n) and y_n = sin(phi_n), with some initial condition (x_0, y_0) = (x, y).
REFERENCES
Carl Schick, Trigonometrie und unterhaltsame Zahlentheorie, Bokos Druck, Zürich, 2003 (ISBN 3-9522917-0-6).
FORMULA
Row polynomials: P(n, y^2) = Product_{j=1..n-1} y_j(y^2), for n >= 1 (the empty product equals 1), where y_j(y^2) = -T^{[j]}(2, y) = -T(2^j, y), the j-th iteration of -T(2, y) = - 1 + 2*y^2, with Chebyshev's T polynomials (A053120).
Row polynomials linearized in T: P(n, y^2) = (-1)^(n-1)*(1/2^(n-2)) * Sum_{m=1..2^(n-2)} T(2*(2^(n-1) + 1 - 2*m), y), for n >= 2, and P(1, y^2) = 1. See the irregular triangle A261693(n-1, m) = 2^(n-1) + 1 - 2*m, n >= 2, 1 <= m <= 2^(n-2).
Irregular triangle: t(n, k) = [y^(2*k)] P(n, y^2), n >= 1, k = 0, 1, ..., 2^(n-1)-1.
EXAMPLE
The irregular triangle T(n, k) begins:
n\k 0 1 2 3 4 5 6 7 ...
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1: 1
2: 1 -2
3: -1 10 -24 16
4: 1 -42 504 -2640 7040 -9984 7168 -2048
...
Row n = 5: -1 170 -8568 201552 -2687360 22573824 -127339520 502081536 -1417641984 2901606400 -4310958080 4600627200 -3435134976 1702887424 -503316480 67108864.
...
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CROSSREFS
KEYWORD
sign,easy,tabf
AUTHOR
Wolfdieter Lang, Nov 19 2019
STATUS
approved