9402807817

Appears in sequences

• Number of words of length 2n-1 generated by the two letters s and t that reduce to the identity 1 by using the relations sssssss=1, tt=1 and stst=1. The generators s and t along with the three relations generate the 14-element dihedral group D7.at n=18A072844
• a(n) = Sum_{k=0..n} binomial(7*n+1,7*k).at n=5A387816
• a(n) = Sum_{k=0..n} binomial(2*n,7*k).at n=18A387845