74280

Appears in sequences

• a(n) is the number of integer strings s(0),...,s(n) counted by array T in A026374 that have s(n)=2; also a(n) = T(2n,n-1).at n=7A026376
• a(n) = Sum_{k=0..n-1} T(n,k) * T(n,k+1), with T given by A026374.at n=7A026947
• a(n) = a(1) + a(2) + ... + a(n-1) - a(m) for n >= 4, where m = n - 1 - 2^p and p is the unique integer such that 2^p < n - 1 <= 2^(p+1), starting with a(1) = 1, a(2) = 2, and a(3) = 3.at n=17A049910
• Number of levels in the compositions of n with odd summands.at n=21A094188
• Triangle read by rows: T(n,k) is the number of Schroeder paths of length 2n and having k peaks at even height.at n=37A101895
• Riordan array (1/sqrt(1-6x+5x^2),(1-3x-sqrt(1-6x+5x^2))/(2x)).at n=37A110165
• Molecular topological indices of the n X n grid graphs.at n=6A192828
• Triangle read by rows: T(n,k) is the number of non-equivalent regular polygons with n+1 edges, one of which is rooted, which are dissected by non-intersecting diagonals into k regions, such that two such polygons are identified up to reflection along the rooted edge and twisting along the diagonals that does not affect the root edge (for 1 <= k <= n-1 and n >= 2).at n=71A232206
• Square array A(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of e.g.f. exp(k*x)*BesselI(1,2*x).at n=74A292628
• Number of canonical forms for separation coordinates on hyperspheres S_n, ordered by increasing number of independent continuous parameters.at n=72A295380
• Triangle read by rows: T(n,k) is the number of labeled point-determining graphs with n nodes and k edges, n >= 0, 0 <= k <= n*(n - 1)/2.at n=49A369283