4537567651

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=17A112849
• Number of set partitions of {1, 2, ..., 2*n} with sizes in {[n, n], [2n]}.at n=18A260878
• 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=17A383431