One more Java solution :)

static long substrCount(int n, String s) {
    long count = 0;
    for (int i = 0; i < s.length(); i++) {
        int innerCounter = 1;

        int counterDown = 0;
        int counterUp = 1;
        while (i - innerCounter >= 0 && i + innerCounter < s.length()
                && s.charAt(i - innerCounter) == s.charAt(i - 1) && s.charAt(i + innerCounter) == s.charAt(i - 1)) {
            count++;
            innerCounter++;
        }

        while (i - counterDown >= 0 && i + counterUp < s.length() && s.charAt(i - counterDown) == s.charAt(i)
                && s.charAt(i + counterUp) == s.charAt(i)) {
            count++;
            counterDown++;
            counterUp++;
        }
    }

    return count + s.length();
}