190899411

Appears in sequences

• a(n) = n*a(n-1) + (n-1)*a(n-2), a(0) = 1, a(1) = 1.at n=11A000255
• Bisection of A000255.at n=5A100445
• Number of permutations of {1,2,...,n} in which the fixed points and the non-fixed points alternate.at n=23A162969
• Triangle read by rows: T(n,k) is the number of permutations of [n] having no 3-sequences and having k successions (0 <= k <= floor(n/2)); a succession of a permutation p is a position i such that p(i +1) - p(i) = 1.at n=42A180185