74002754276domain: NAppears in sequencesExpansion of x/((1 + x^2)*(1 - 4*x + x^2)).at n=20A099486Numbers n such that the sum of the hexagonal numbers H(n) and H(n+1) is equal to the sum of the pentagonal numbers P(m) and P(m+1) for some m.at n=4A251990