122640

Appears in sequences

• Let sigma_m (n) be result of applying sum-of-divisors function m times to n; call n (m,k)-perfect if sigma_m (n) = k*n; sequence gives the (3,k)-perfect numbers.at n=32A019292
• Number of ternary irreducible monic polynomials of degree n; dimensions of free Lie algebras.at n=13A027376
• Product_{k>=1} 1/(1 - x^k)^a(k) = 1 + 3x.at n=12A038064
• Product_{k>=1}(1 + x^k)^a(k) = 1 + 3x.at n=12A038068
• Numbers n such that phi(sigma(n)) = 5*phi(n).at n=18A067708
• Expansion of 1/(1 - 2*x - 2*x^2 - 3*x^3).at n=11A077834
• Number of "sets of even lists" for even n, cf. A000262.at n=4A088026
• a(n) = floor(3^n / n).at n=12A092763
• Consider iteration of the function f(x) = sigma(phi(x)) = A062402(x). Sequence lists the numbers k such that the trajectory of k returns to k.at n=42A096998
• Number of necklaces with n beads of 4 colors, no 2 adjacent beads the same color.at n=12A106366
• a(n) + a(n+1) + a(n+2) = 3^n.at n=12A152733
• Expansion of e.g.f. exp(t*x)/(1 - x^2/t^2 - t^3* x^3).at n=72A158757
• Expansion of e.g.f.: exp(t*x)/(1 - x^2/t - t^3*x^3).at n=54A158785
• Dimensions of primitive Lie algebras connected with the Mantaci-Reutenauer algebra MR^(2).at n=12A185171
• Triangular array read by rows. T(n,k) is the number of partial permutations (injective partial functions) of {1,2,...,n} that have exactly k elements in a cycle. The k elements are not necessarily in the same cycle. A fixed point is considered to be in a cycle.at n=40A206703
• Floor((3^n-1)/n).at n=12A225585
• Triangle defined by g.f. A(x,y) = exp( Sum_{n>=1} x^n/n * Sum_{k=0..n} binomial(n^2, k^2) * y^k ), as read by rows.at n=38A228902
• Numbers of the form (3^k - 3)/k.at n=7A247033
• Number of 6-cycles in the n-tetrahedral graph.at n=6A289794
• Positive solution to 2^(n-1) = (1/n) * Sum_{d|n} a(d) * a(n/d).at n=14A299119