20321280

Appears in sequences

• Number of aperiodic necklaces with n labeled beads of 2 colors.at n=8A032321
• Expansion of e.g.f. (2-2*x-x^2)/((1-x)*(1-x-x^2)).at n=9A052660
• a(n) = [n/1][n/2][n/3] ...[n/n] / n^(tau(n)/2).at n=28A076891
• Triangle T(n,k) = n!*binomial(n-1, k-1) for 1 <= k <= n, read by rows.at n=39A156992
• Triangle T(n,k) = n!*binomial(n-1, k-1) for 1 <= k <= n, read by rows.at n=41A156992
• G.f.: Sum_{n>=0} (n+x)^n * x^n / (1 + n*x + x^2)^n.at n=10A187742
• a(n) = 12*a(n-1) - 12*a(n-2), a(0)=0, a(1)=1.at n=8A190873
• Number of ways to arrange n books on 4 consecutive bookshelves, leaving no shelf empty.at n=5A200979
• Vandermonde determinant of the first n terms of (1,2,4,8,16,...).at n=4A203303
• Greatest common divisors of consecutive floor-factorial numbers (A010786).at n=27A208448
• Sum of divisors of colossally abundant numbers.at n=11A215640
• If n mod 2 = 0 then 2^n*3^(n-1)+2^(n+1)*3^(n/2-1) otherwise 2^n*3^(n-1)+2^n*3^((n-1)/2).at n=10A232493
• Number m that give records for the quotient between the maximum and minimum x's such that sigma(x)=m.at n=27A241854
• Number of permutations of {1,2,3,...,n} such that no multiples of 3 are adjacent.at n=11A258216
• Triangle read by rows, T(n,k) with n,k > 1, is the number of subsequences of length k over all permutations of [n], which are neither increasing or decreasing.at n=29A373766
• Vandermonde determinant of the divisors of n.at n=15A389552