1. Online encyclopedia of integer sequences, A249665, https://oeis.org/A249665.
2. Online encyclopedia of integer sequences, A000930, https://oeis.org/A000930.
3. On uniquely k-determined permutations;Avgustinovich;Discrete Math.,2008
4. Spectra of digraphs;Brualdi;Linear Algebra Appl.,2010
5. Analytic Combinatorics;Flajolet,2009