a(n) is the number of words of length n over the alphabet [n] and sortable by a (2,1)-pop stack of depth 2.

A369327

a(n) is the number of words of length n over the alphabet [n] and sortable by a (2,1)-pop stack of depth 2.

Terms

    a(0) =1a(1) =1a(2) =4a(3) =24a(4) =149a(5) =923a(6) =5784a(7) =36708a(8) =235156a(9) =1516864a(10) =9838018a(11) =64093998a(12) =419137378a(13) =2749637566a(14) =18087479624a(15) =119263349200a(16) =788015054253

External references