$a, b, c$  are real numbers. Find all triangles with sides $a^n, b^n, c^n$  for all natural number n.
To find all triangles with sides \(a^n, b^n, c^n\) for all natural numbers \(n\), we need to ensure that the triangle inequality holds for all \(n\). The triangle inequality states that for any triangle with sides \(x, y, z\):

\[ x + y > z \]
\[ x + z > y \]
\[ y + z > x \]

Given sides \(a^n, b^n, c^n\), we need to check if these inequalities hold for all \(n\).

1. **Assume \(a \neq b \neq c\) and without loss of generality, let \(a > b > c\):**

   - For \(n = 1\), the inequalities are:
     \[ a < b + c \]
     \[ b < a + c \]
     \[ c < a + b \]

   - For \(n = 2\), the inequalities are:
     \[ a^2 < b^2 + c^2 \]
     \[ b^2 < a^2 + c^2 \]
     \[ c^2 < a^2 + b^2 \]

   - For \(n = 3\), the inequalities are:
     \[ a^3 < b^3 + c^3 \]
     \[ b^3 < a^3 + c^3 \]
     \[ c^3 < a^3 + b^3 \]

   - And so on for all \(n\).

   However, if \(a > b > c\), then \(a^n > b^n > c^n\) for all \(n\). This implies:
   \[ a^n > b^n + c^n \]
   which violates the triangle inequality \(a^n < b^n + c^n\). Therefore, \(a \neq b \neq c\) cannot form a triangle for all \(n\).

2. **Consider the case where two sides are equal, say \(a = b\):**

   - Let \(a = b > c\):
     \[ a^n = b^n \]
     \[ a^n < b^n + c^n \]
     \[ b^n < a^n + c^n \]
     \[ c^n < a^n + b^n \]

   Since \(a^n = b^n\), the inequalities reduce to:
     \[ a^n < a^n + c^n \]
     \[ c^n < a^n + a^n \]
     \[ c^n < 2a^n \]

   These inequalities hold for all \(n\) if \(a > c\).

3. **Consider the case where all three sides are equal, \(a = b = c\):**

   - Let \(a = b = c\):
     \[ a^n = b^n = c^n \]

   The triangle inequalities become:
     \[ a^n < a^n + a^n \]
     \[ a^n < a^n + a^n \]
     \[ a^n < a^n + a^n \]

   These inequalities are always true for all \(n\).

Therefore, the only triangles that satisfy the triangle inequality for all \(n\) are those where either two sides are equal or all three sides are equal.

The final answer is \( \boxed{ a = b > c } \) or \(a = b = c\).