20487

Appears in sequences

• Trisection of A007294.at n=39A073471
• G.f.: A(x) = exp( Sum_{n>=1} sigma(n)^2*x^n/n ), a power series in x with integer coefficients.at n=13A156302
• Number of rooted forests with n nodes in which each component contains at least two nodes.at n=13A174145
• Number of nondecreasing arrangements of n numbers in -6..6 with sum zero and sum of squares not greater than n*42/3.at n=10A183924
• Potential magic constants of 9 X 9 magic squares composed of consecutive primes.at n=35A191679
• Number of ordered triples (w,x,y) with all terms in {1,...,n} and w^2>x^2+y^2.at n=43A211637
• Numbers of the form k + wt(k) for exactly four distinct k, where wt(k) = A000120(k) is the binary weight of k.at n=2A227915
• Odd numbers k such that phi(k) and cototient(k) have the same prime signature.at n=25A280927
• G.f. A(x) satisfies: Sum_{n>=0} A(x)^((n+1)^2) * x^n = Sum_{n>=0} (1 + A(x)^(n+2))^n * x^n.at n=7A326287
• Square array A(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where column k is the expansion of B(x)^k, where B(x) is the g.f. of A213093.at n=63A384866