4667212440

Appears in sequences

• Twice central binomial coefficients.at n=17A028329
• Number of n-step walks on a line starting from the origin but not returning to it.at n=35A063886
• A Catalan transform of (1 + 2*x)/(1 - 2*x).at n=17A100320
• Number of n X n (-1,1)-circulant matrices with determinant 0.at n=34A144926
• a(n) = number of n-lettered words in the alphabet {1, 2} with as many occurrences of the substring (consecutive subword) [1, 1] as of [2, 2].at n=36A182027
• Number of permutations of length n such that numbers at odd positions are monotone and numbers at even positions are also monotone.at n=33A257546
• a(n) is the number of permutations of length n that avoid the pattern 321 and the mesh pattern (12, 189) or the same sequence for the mesh patterns (12, 243), (12, 378), (12, 414).at n=20A289595
• Number of tieless quidditch games with n scoring events.at n=34A335974