2821728

Appears in sequences

• a(n) = Sum_{j=0..n} A047072(j, n-j).at n=24A047073
• a(n) = 4*C(2n,n) - 3*0^n.at n=11A146534
• a(n) = 4*(2*n)! / (n!)^2.at n=11A240530
• Number of permutations of length n such that numbers at odd positions are monotone and numbers at even positions are also monotone.at n=22A257546
• a(0) = 1; for n >= 1, a(n) = A059897(n, a(n-1)).at n=22A284567