56871domain: NAppears in sequencesNumbers n not of the form i^2+(i+1)^2 such that there are integers a < b with a^2+(a+1)^2+...+(n-1)^2 = n^2+(n+1)^2+...+b^2.at n=27A094523Engel expansion of the Dottie number, A003957.at n=18A182503a(1) = 1; a(n) = -Sum_{k=2..n} k^3 * a(floor(n/k)).at n=40A360658