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A086389
Number of factors over Q in the factorization of U_n(x) - 1 where U_n(x) is the Chebyshev polynomial of the second kind.
1
1, 1, 2, 3, 2, 3, 3, 4, 3, 4, 2, 6, 4, 3, 4, 6, 2, 6, 4, 6, 4, 4, 3, 8, 5, 4, 4, 8, 2, 7, 4, 6, 6, 5, 4, 9, 4, 4, 4, 10, 2, 8, 6, 6, 6, 4, 3, 11, 5, 6, 4, 8, 4, 8, 6, 8, 4, 6, 2, 12, 6, 3, 8, 9, 4, 8, 4, 8, 4, 9, 2, 12, 6, 4, 8, 8, 4, 8, 5, 10, 5, 6, 4, 12, 6
OFFSET
1,3
LINKS
Gerzson Kéri, The factorization of compressed Chebyshev polynomials and other polynomials related to multiple-angle formulas, Annales Univ. Sci. Budapest (Hungary, 2022) Sect. Comp., Vol. 53, 93-108.
PROG
(PARI) a(n)={vecsum(factor(polchebyshev(n, 2, x)-1)[, 2])} \\ Andrew Howroyd, Jul 10 2018
CROSSREFS
Cf. A086375.
Sequence in context: A319982 A304331 A241834 * A128622 A026256 A079715
KEYWORD
nonn
AUTHOR
Yuval Dekel (dekelyuval(AT)hotmail.com), Sep 08 2003
EXTENSIONS
a(21)-a(85) from Andrew Howroyd, Jul 10 2018
STATUS
approved