Duplicate of A009585.

A012270

Duplicate of A009585.

Terms

    a(0) =0a(1) =0a(2) =2a(3) =6a(4) =22a(5) =100a(6) =668a(7) =6048a(8) =64776a(9) =763488a(10) =9676152a(11) =131167080a(12) =1900043880

External references