24382domain: NAppears in sequencesNumbers k such that sigma(k) = phi(k+1) + phi(k-1).at n=7A068401a(n) = n! * Sum_{k=0..floor(n/4)} (-n/24)^k /(k! * (n-4*k)!).at n=9A362345Centered 27-gonal numbers.at n=42A389797