335922domain: NAppears in sequencesa(n) = Sum_{j=1..n} phi(n)^j.at n=6A075490a(0)=0; a(n) = 6*a(n-1) + 6.at n=7A105281Number of reduced words of length n in Coxeter group on 3 generators S_i with relations (S_i)^2 = (S_i S_j)^7 = I.at n=18A164352a(n) = Sum_{k=1..7} n^k.at n=6A228291