100904domain: NAppears in sequencesExpansion of the g.f. (x^2-x+1)*(x^2-3*x+3)/(x-1)^6.at n=23A257890G.f. satisfies A(x) = ( 1 + x / (1 - x*A(x)^3)^2 )^2.at n=7A371615Numerator of sum of reciprocals of all prime divisors of all positive integers <= n.at n=15A380314a(n) = Sum_{k=0..n} (-1)^k * binomial(5*n-k+4,n-k).at n=5A390593