I can build the xp to level table from memory, because it's constructed such that you need your current level x 1000 xp to reach the next level.
Level 1-2: 1000 xp
2-3: 3000 xp (2000 gained)
3-4: 6000 xp (3000 gained)
4-5: 10,000 xp (4000 gained)
etc...
EDIT: You can even make it a function. Since most times it comes up will be the minimum xp to be level x, you would have to subtract 1 from that level to find the xp value, like so:
[sum (level -1)] x 1000 = minimum xp to be [level].
So, your DM says you're starting a game with the minimum xp for level 8 (in case you have LA, LA buyoff, want to item craft, etc... and start lower level). How much xp do you have? (1+2+3+4+5+6+7) x 1000 = 28,000 xp.
Note, starting at level 1 gives sum (1-1) x 1000 = 0. You need no xp to be level 1.