1 Loop & 1 StringBuilder

Pattern.java

public class Pattern {
    public static void main(final String[] args) {
        final StringBuilder sb = new StringBuilder();
        for (int i = 1; i <= 7; i++) {
            System.out.println(String.format("%s %s %s", sb.toString(), i, sb.reverse()));
            sb.reverse().append(" " + i);
        }
    }
}