Number of chiral pairs of set partitions of a primitive cycle of n elements having exactly two different elements.

A308706

Number of chiral pairs of set partitions of a primitive cycle of n elements having exactly two different elements.

Terms

    a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =1a(8) =2a(9) =7a(10) =12a(11) =31a(12) =58a(13) =126a(14) =233a(15) =484a(16) =904a(17) =1800a(18) =3395a(19) =6643a(20) =12612a(21) =24457a(22) =46655a(23) =90157a(24) =172750a(25) =333498a(26) =641214a(27) =1238664a(28) =2388618a(29) =4620006

External references