269128937221
domain: N
Appears in sequences
- Number of congruence classes (epimorphisms/vertex partitionings induced by graph endomorphisms) of undirected cycles of even length: |C(C_{2*n})|.at n=20A112849
- Number of set partitions of {1, 2, ..., 2*n} with sizes in {[n, n], [2n]}.at n=21A260878
- a(n) is the denominator of tanh(Sum_{k=1..n-1} artanh(k/n)), where artanh is the inverse hyperbolic tangent function.at n=20A383431