a(n) is the number of chains from {} to a top element in the poset of even sized subsets of {1,2,...,n} ordered by inclusion.

A336012

a(n) is the number of chains from {} to a top element in the poset of even sized subsets of {1,2,...,n} ordered by inclusion.

Terms

    a(0) =1a(1) =1a(2) =1a(3) =3a(4) =7a(5) =35a(6) =121a(7) =847a(8) =3907a(9) =35163a(10) =202741a(11) =2230151a(12) =15430207a(13) =200592691a(14) =1619195761a(15) =24287936415a(16) =224061282907

External references