%I #12 Dec 02 2020 07:21:57
%S 1,1,2,4,8,18,45,119
%N a(n) = number of permutations avoiding the simsum pattern 213 and the classical pattern 321.
%H Marilena Barnabei, Flavio Bonetti, Niccolò Castronuovo, Matteo Silimbani, <a href="https://doi.org/10.37236/9482">Permutations avoiding a simsun pattern</a>, The Electronic Journal of Combinatorics (2020) Vol. 27, Issue 3, P3.45. See Section 4.3.
%K nonn,more
%O 0,3
%A _N. J. A. Sloane_, Dec 01 2020.