OFFSET
0,3
COMMENTS
For n > 0, a(n) is the square of the determinant of the (2*n) X (2*n) matrix with elements M(j,k) = cos(Pi*j*k/n). See the MathOverflow link. - Hugo Pfoertner, Sep 18 2021
LINKS
Joerg Arndt, Table of n, a(n) for n = 0..100
Zhi-Wei Sun, Fedor Petrov, A surprising identity, discussion in MathOverflow, Jan 17 2019.
FORMULA
a(n) = n! * [x^n] -LambertW(-n*x). - Ilya Gutkovskiy, Oct 04 2017
a(n) = A089072(2*n-1, n), n >= 1. - G. C. Greubel, Nov 01 2022
MATHEMATICA
Join[{0}, Table[n^(2 n - 1), {n, 20}]] (* Harvey P. Dale, May 16 2016 *)
PROG
(PARI) a(n) = if(n==0, 0, n^(2*n-1)) \\ Altug Alkan, Oct 04 2017
(Magma) [n eq 0 select 0 else n^(2*n-1): n in [0..30]]; // G. C. Greubel, Nov 01 2022
(SageMath) [0]+[n^(2*n-1) for n in range(1, 31)] # G. C. Greubel, Nov 01 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jul 05 2003
STATUS
approved