91505domain: NAppears in sequencesNumbers k such that sigma(phi(sigma(k))) = phi(sigma(phi(k))).at n=26A067160a(n) = s(2*n) where s(0) = 0, s(1) = s(2) = 1, s(n) = abs(Sum_{k=2..n-1} (-1)^k * s(n-k) * s(k)).at n=49A072851Number of permutations p of [n] such that p(i) > p(i+1) iff i == 1 (mod 8).at n=16A250264