19905

Appears in sequences

• a(n) = dot_product(n,n-1,...2,1)*(5,6,...,n,1,2,3,4).at n=40A026060
• Number of pairs of partitions of [n] whose join is the partition {{1,2,...,n}}.at n=6A060639
• Number of polyominoes with n cells that tile the plane by translation or by 180-degree rotation (Conway criterion).at n=11A075203
• Number of invertible circulant (0,1) matrices over the reals that have even determinant.at n=14A086479
• Expansion of g.f. (1 + x + 2*x^2)/((1 - x)^3*(1 - x^3)).at n=43A092498
• Number of n X n binary arrays symmetric under horizontal and vertical reflection with all ones connected only in a 111-110-111 pattern in any orientation.at n=14A146282
• Numbers k such that k^6 - 2 and k^6 + 2 are both primes.at n=28A154938
• Principal diagonal of the convolution array A213822.at n=14A213823
• Triangle T(n, k) = Numbers of inequivalent (mod D_3) ways to place k points on a triangular grid of side n so that no three of them are vertices of an equilateral triangle of any orientation. Triangle read by rows.at n=39A243141
• Molien series for invariants of finite Coxeter group A_9.at n=60A266778
• Regular triangle where T(n,k) is the number of pairs of set partitions of {1,...,n} with join of length k.at n=15A318392
• Number of nonisomorphic semigroups with n elements satisfying the equation xyz = xz.at n=21A390162