Task: Brazilian numbers
C: #include <stdio.h>

typedef char bool;

#define TRUE 1
#define FALSE 0

bool same_digits(int n, int b) {
    int f = n % b;
    n /= b;
    while (n > 0) {
        if (n % b != f) return FALSE;
        n /= b;
    }
    return TRUE;
}

bool is_brazilian(int n) {
    int b;
    if (n < 7) return FALSE;
    if (!(n % 2) && n >= 8) return TRUE;
    for (b = 2; b < n - 1; ++b) {
        if (same_digits(n, b)) return TRUE;
    }
    return FALSE;
}

bool is_prime(int n) {
    int d = 5;
    if (n < 2) return FALSE;
    if (!(n % 2)) return n == 2;
    if (!(n % 3)) return n == 3;
    while (d * d <= n) {
        if (!(n % d)) return FALSE;
        d += 2;
        if (!(n % d)) return FALSE;
        d += 4;
    }
    return TRUE;
}

int main() {
    int i, c, n;
    const char *kinds[3] = {" ", " odd ", " prime "};    
    for (i = 0; i < 3; ++i) {
        printf("First 20%sBrazilian numbers:\n", kinds[i]);
        c = 0;
        n = 7;
        while (TRUE) {
            if (is_brazilian(n)) {
                printf("%d ", n);
                if (++c == 20) {
                    printf("\n\n");
                    break;
                }
            }
            switch (i) {
                case 0: n++; break;
                case 1: n += 2; break;
                case 2: 
                    do {
                        n += 2;
                    } while (!is_prime(n));
                    break;
            }
        }
    }

    for (n = 7, c = 0; c < 100000; ++n) {
        if (is_brazilian(n)) c++; 
    }
    printf("The 100,000th Brazilian number: %d\n", n - 1);
    return 0;
}

Go: package main

import "fmt"

func sameDigits(n, b int) bool {
    f := n % b
    n /= b
    for n > 0 {
        if n%b != f {
            return false
        }
        n /= b
    }
    return true
}

func isBrazilian(n int) bool {
    if n < 7 {
        return false
    }
    if n%2 == 0 && n >= 8 {
        return true
    }
    for b := 2; b < n-1; b++ {
        if sameDigits(n, b) {
            return true
        }
    }
    return false
}

func isPrime(n int) bool {
    switch {
    case n < 2:
        return false
    case n%2 == 0:
        return n == 2
    case n%3 == 0:
        return n == 3
    default:
        d := 5
        for d*d <= n {
            if n%d == 0 {
                return false
            }
            d += 2
            if n%d == 0 {
                return false
            }
            d += 4
        }
        return true
    }
}

func main() {
    kinds := []string{" ", " odd ", " prime "}
    for _, kind := range kinds {
        fmt.Printf("First 20%sBrazilian numbers:\n", kind)
        c := 0
        n := 7
        for {
            if isBrazilian(n) {
                fmt.Printf("%d ", n)
                c++
                if c == 20 {
                    fmt.Println("\n")
                    break
                }
            }
            switch kind {
            case " ":
                n++
            case " odd ":
                n += 2
            case " prime ":
                for {
                    n += 2
                    if isPrime(n) {
                        break
                    }
                }
            }
        }
    }

    n := 7
    for c := 0; c < 100000; n++ {
        if isBrazilian(n) {
            c++
        }
    }
    fmt.Println("The 100,000th Brazilian number:", n-1)
}