Articles — Page 4

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

院角那株不知名的树，自漫长阴雨时节便浸在阴翳里。我总在窗前半掩着帘，看它瘦削的枝桠将天色裁成淡墨的写意，恍若故纸堆里褪了色的水墨小品。

We consider the radial differential operator for a fixed angular mode \(n\), ∑ Formula

We introduce azimuthal Fourier expansion for functions with circular symmetry: we write \(f(r, \phi)\) as a sum of angular modes ∑ Formula, where ∑ Formula is obtained by integrati…

Hankel–Bessel Ladder Identities Claim. For suitable \(f_m(r)\) and \(k>0\), ∑ Formula Here ∑ Formula.