OFFSET
0,2
REFERENCES
Per Hakan Lundow, "Computation of matching polynomials and the number of 1-factors in polygraphs", Research report, No 12, 1996, Department of Math., Umea University, Sweden.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..200
Alois P. Heinz, G.f. for A028482
Per Hakan Lundow, Enumeration of matchings in polygraphs, 1998.
FORMULA
G.f.: see link above.
a(n) = 2^n * sqrt(Resultant(U_{2*n}(x/2), T_{11}(i*x/2))), where T_n(x) is a Chebyshev polynomial of the first kind, U_n(x) is a Chebyshev polynomial of the second kind and i = sqrt(-1). - Seiichi Manyama, Apr 17 2020
PROG
(PARI) {a(n) = sqrtint(4^n*polresultant(polchebyshev(2*n, 2, x/2), polchebyshev(11, 1, I*x/2)))} \\ Seiichi Manyama, Apr 17 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved