Harmonic functions of the form $f(x^2+y^2)$
96303
When does $h(x^2+y^2)$ be harmonic?
69734
how to find all functions such that $f\left( x^{2} - y^{2} \right) = ( x - y )( f(x) + f(y) )$
156778
Finding functions satisfying $f(f(x))+f(x)+x=0$
20945
On a series involving harmonic numbers
151297
Second order partial of $f(x,y)=\frac{xy(x^2-y^2)}{x^2+y^2}$
409
functions satisfying $f(x - y) = f(x) f(y) - f(a - x) f(a + y)$ and $f(0)=1$
94489
Mean value property implies harmonicity
23186
$f: \mathbb{R^2} \to \mathbb{R}$ a $C^\infty$ function such that $f(x,0)=f(0,y)=0$ then exists $g$ such that $f(x,y)=xy\, g(x,y)$
120533
A harmonic function with sublinear growth at infinity is constant
130047
Is it possible to use regularization methods on the Harmonic Series?
75932
Differentiability of $g:=f(\sqrt{x^2+y^2})$ for a $C^1$ function with $f'(0)=0$ NBHM $2008$
29403
Finding functions $f: \Bbb R_*^+ \to \Bbb R_*^+$ with certain properties
88097
Fourier series for $f(x)=(\pi -x)/2$
98363
Expanding two-variable function $f(x,y)$ over the complete sets $\{ g_{i}(x) \}$ and $\{ h_{j}(y) \}$
8039
an analytic function from unit disk to unit disk with two fixed point
84346
homogeneous nonlinear functions
37976
Find all functions $f$ such that $(x+y)f(x)+f(y^2)=(x+y)f(y)+f(x^2)$