Number of degree-n permutations of order exactly 3.

Terms

a(0) =0a(1) =0a(2) =0a(3) =2a(4) =8a(5) =20a(6) =80a(7) =350a(8) =1232a(9) =5768a(10) =31040a(11) =142010a(12) =776600a(13) =4874012a(14) =27027728a(15) =168369110a(16) =1191911840a(17) =7678566800a(18) =53474964992a(19) =418199988338