Math
posted by David .
Hello. I am trying to help out my sister and find patterns in numbers....
Ex/ 1+2
2+2
3+2
4+2
My question is... I can't figure out what the pattern is in the following set...
1 goes to 4
2 goes to 7
3 goes to 10
and 4 goes to 13......
I initially thought that it was 3x + 2 but it does not work for the third. Can you help?

1 + 3 = 4
2 + 5 = 7
3 + 7 = 10
4 + 9 = 13
5 + ? = 16
You might show her with subtraction:
4  1 = ?
7  2 = ?