28160

Appears in sequences

• a(n) = n*(n+1)*2^(n-2).at n=10A001788
• Triangle of tangent numbers.at n=21A008308
• Triangle of coefficients in expansion of sin(n*x) (or sin(n*x)/cos(x) if n is even) in ascending powers of sin(x).at n=53A028298
• Numbers k that divide the (left) concatenation of all numbers <= k written in base 21 (most significant digit on left).at n=12A029490
• Coordination sequence for diamond structure D^+_10. (Edges defined by l_1 norm = 1.)at n=7A035881
• Weights of rotation-symmetric functions in n variables.at n=13A051253
• Numbers that can be written as k/d(k) in four or more ways, where d(k) = number of divisors of k.at n=2A051346
• Duplicate of A051346.at n=2A051520
• Triangle T(n,k) (1 <= k <= n) of tangent numbers, read by rows: T(n,k) = coefficient of x^n/n! in expansion of (tan x)^k/k!.at n=38A059419
• A diagonal of A059419.at n=3A059420
• a(n) = 2*a(n-1) + 4*a(n-2), a(0)=1, a(1)=2.at n=9A063727
• 11-almost primes (generalization of semiprimes).at n=30A069272
• Horadam sequence (0,1,4,2).at n=10A085449
• Triangle read by rows: T(n,k) is the number of Dyck paths of semilength n, having k ddu's [here u = (1,1) and d = (1,-1)].at n=38A091894
• a(n) = 2^(2n+1) * binomial(3n,n)/(2n+1).at n=4A098272
• a(n) = 2 + floor((1 + Sum_{j=1..n-1} a(j))/3).at n=33A120149
• Number of permutations of n distinct letters (ABCD...) each of which appears 4 times and having n-3 fixed points.at n=11A123293
• Number of ternary Lyndon words with exactly four 1's.at n=8A124722
• Adjacent-to-central terms of even-indexed rows of triangle A125806: a(n) = A125806(2n+2,n).at n=5A125808
• Row 11 of A038207.at n=2A135290