Table of n, a(n) for n=1..4.
Eric Weisstein's World of Mathematics, Eulerian Cycle
Eric Weisstein's World of Mathematics, Sun Graph
Sequence in context: A298202 A333863 A300197 * A051675 A288951 A175988
Adjacent sequences: A297383 A297384 A297385 * A297387 A297388 A297389
Eric W. Weisstein, Dec 29 2017
a(3) from Andrew Howroyd, Jan 11 2018
a(4) from Andrew Howroyd, May 22 2020