28140

Appears in sequences

• a(n) is the concatenation of n and 5n.at n=27A019553
• a(n) = n*(n+1)*(n^2 + 2)/6.at n=20A071239
• a(n) = 3*n^3 + n^2 - 4*n.at n=21A083127
• E.g.f.: A(x) = Product_{n>=1} (1 + x^n/n)^n.at n=7A181541
• 1/4 the number of n X n 0..3 symmetric matrices with every element equal to one, two or four horizontal and vertical neighbors.at n=4A211089
• Smallest number k such that prime(n) is the n-th divisor of k.at n=17A221647
• a(n) = n*(n+1)*(7*n-6)/2.at n=20A256718
• Square array A(n,k) (n>=1, k>=1) read by antidiagonals: A(n,k) is the number of n-colorings of the prism graph Y_k on 2k vertices.at n=42A277443
• T(n, k) = [x^k] n! [t^n] 1/(exp((V*(2 + 2*t + V))/(4*t))*sqrt(1 + V)) where V = W(-2*t*x) and W denotes the Lambert function. Table read by rows, T(n, k) for 0 <= k <= n.at n=31A343806