OFFSET
0,2
COMMENTS
a(n)/4^n is the square of the determinant of a (2*n+1) X (2*n+1) matrix with elements M(j,k) = cos(Pi*j*k/n). See the MathOverflow link. - Hugo Pfoertner, Sep 18 2021
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..190
Zhi-Wei Sun, Fedor Petrov, A surprising identity, discussion in MathOverflow, Jan 17 2019.
FORMULA
From Mathew Englander, Aug 14 2020: (Start)
a(n) = A085527(n)^2.
a(n) = A085529(n)/(2*n + 1).
(End)
From Alois P. Heinz, Aug 14 2020: (Start)
a(n) = A016754(n)^n.
MATHEMATICA
Table[(2 n + 1)^(2 n), {n, 0, 20}] (* Vincenzo Librandi, Feb 26 2013 *)
PROG
(Magma) [(2*n+1)^(2*n): n in [0..13]]; // Vincenzo Librandi, Feb 26 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jul 05 2003
STATUS
approved