random(x*7)-function only gives smaller multiples of 7 on first call

Hi,

```
int n;

void setup() {
Serial.begin(9600);
randomSeed(analogRead(A0));
n = random(21);
Serial.println(n);
}
void loop() {
}
```
only outputs numbers from the set: {0,7,21}. All multiples of seven give back the smaller multiples of seven on the first call. I tested on arduino-hardware and on tinkercad (simulation).

incerely yours
shanty

Start by reproducing the sketch in setup() with randomSeed(analogRead(A0)) and random(21), then inspect the random() and randomSeed() entry points in ArduinoCore-avr. Compare the first-call output with subsequent calls and verify that the reported restriction no longer occurs across the Arduino hardware and Tinkercad cases described.

Written by the indexing model from the issue text.