

A125076


Triangle with trigonometric properties,


5



1, 1, 2, 1, 3, 5, 1, 5, 8, 13, 1, 6, 19, 21, 34, 1, 8, 25, 65, 55, 89, 1, 9, 42, 90, 210, 144, 233, 1, 11, 51, 183, 300, 654, 377, 610, 1, 12, 74, 234, 717, 954, 1985, 987, 1597, 1, 14, 86, 394, 951, 2622
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OFFSET

1,3


COMMENTS

This triangle is #3 in an infinite set, where Pascal's triangle = #2. Generally, the infinite set is constrained by two properties: For triangle N, row sums are powers of N and upward sloping diagonals have roots equal to N + 2*cos(2*Pi/Q).
The triangle may be constructed by considering the rows of A152063 as upward sloping diagonals.  Gary W. Adamson, Nov 26 2008


LINKS



FORMULA

Upward sloping diagonals are alternating (unsigned) characteristic polynomial coefficients of two forms of matrices: all 1's in the super and subdiagonals and (2,3,3,3,...) in the main diagonal and the other form all 1's in the super and subdiagonals and (3,3,3,...) in the main diagonal.


EXAMPLE

First few rows of the triangle are:
1;
1, 2;
1, 3, 5;
1, 5, 8, 13;
1, 6, 19, 21, 34;
1, 8, 25, 65, 55, 89;
1, 9, 42, 90, 210, 144, 233;
...
For example, the upwardsloping diagonal (1, 8, 19, 13) is derived from x^3  8x^2 + 19x  13, characteristic polynomial of the 3 X 3 matrix [2, 1, 0; 1, 3, 1;, 0, 1, 3], having an eigenvalue of 3 + 2*cos(2*Pi/7). The next upwardsloping diagonal is (1, 9, 25, 21), derived from the characteristic polynomial x^3  9x^2 + 25x  21 and the matrix [3, 1, 0; 1, 3, 1; 0, 1, 3]. An eigenvalue of this matrix and a root of the corresponding characteristic polynomial is 4.414213562... = 3 + 2*cos(2*Pi/8).


CROSSREFS



KEYWORD



AUTHOR



STATUS

approved



