Number of arithmetical structures on D_n.

Terms

a(0) =14a(1) =46a(2) =176a(3) =620a(4) =2218a(5) =7938a(6) =28572a(7) =103384a(8) =376056a(9) =1374680a(10) =5048348a(11) =18618290a(12) =68932582a(13) =256133188a(14) =954856744a(15) =3570492960a(16) =13388550056a(17) =50334109160a(18) =189684561610a(19) =716420218810