81811

Appears in sequences

• The Wiener index of the graph \|/_\/_\/_..._\/_\|/ having n nodes on the horizontal path.at n=34A180571
• Semiprimes formed by concatenating n, n, and 1 for n = 1, 2, 3,....at n=33A210711
• Total number of nodes summed over all lattice paths from (0,0) to (n,n) using steps {(k,0), (0,k) | 0<k<=4} which never go above the diagonal x=y.at n=6A286918