Number of elements in the mutation class of a quiver of type D_n.

Terms

a(0) =4a(1) =6a(2) =26a(3) =80a(4) =246a(5) =810a(6) =2704a(7) =9252a(8) =32066a(9) =112720a(10) =400024a(11) =1432860a(12) =5170604a(13) =18784170a(14) =68635478a(15) =252088496a(16) =930138522a(17) =3446167860a(18) =12815663844a(19) =47820447028a(20) =178987624514a(21) =671825133648