Number of commuting 4-tuples of elements from S_n, divided by n!.

Terms

a(0) =1a(1) =8a(2) =21a(3) =84a(4) =206a(5) =717a(6) =1810a(7) =5462a(8) =13859a(9) =38497a(10) =96113a(11) =253206a(12) =620480a(13) =1566292a(14) =3770933a(15) =9212041a(16) =21768608a(17) =51795427a(18) =120279052a(19) =279849177a(20) =639379257a(21) =1459282932a(22) =3283758256a(23) =7369471795a(24) =16351101855a(25) =36147590987a(26) =79162129897a(27) =172646751524a(28) =373527250619a(29) =804631686843