20801200

Appears in sequences

• Twice central binomial coefficients.at n=13A028329
• a(n) = Sum_{j=0..n} A047072(j, n-j).at n=27A047073
• Number of n-step walks on a line starting from the origin but not returning to it.at n=27A063886
• A Catalan transform of (1 + 2*x)/(1 - 2*x).at n=13A100320
• Number of n X n (-1,1)-circulant matrices with determinant 0.at n=26A144926
• 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=28A182027
• Number of permutations of length n such that numbers at odd positions are monotone and numbers at even positions are also monotone.at n=25A257546
• Number of tieless quidditch games with n scoring events.at n=26A335974