From StrategyWiki, the free strategy guide and walkthrough wiki

This is a general list of the experience required to gain each level. The number may not be exact, but will give the general neighborhood of each level.

Level	Experience		Experience
1	0		51	200000
2	1000		52	207250
3	2000		53	214500
4	3250		54	229500
5	4500		55	237250
6	6000		56	245000
7	7500		57	253000
8			58	261000
9	11000		59	269000
10	13000		60
11			61	277500
12			62	285000
13			63	294500
14			64	303250
15			65	312000
16			66	321000
17			67
18			68	339250
19			69
20			70
21	42500		71
22	45000		72
23	49500		73	387000
24	53250		74	397000
25	57000		75	407000
26	61000		76	417250
27	65000		77	427500
28	69250		78	438000
29	73500		79	448500
30	78000		80	459250
31			81	470000
32			82
33			83	492250
34			84	503250
35			85	514500
36			86	526000
37			87	537500
38	118000		88	549250
39	123500		89	561000
40	129250		90	573000
41	135250		91	585000
42	141000		92	597250
43	147000		93	609500
44	153250		94	622000
45	165000		95	634750
46			96
47	172500		97
48	129250		98	675000
49	185000		99	686000
50	198000

Note: The blank ones I don’t have, either because they didn’t look right, or I couldn’t find where I wrote them down. They’ll be there in future revisions.

For those of you who care about such things, the equation of the trendline was:

 y = 61.285x^2 + 869.16x - 2016.6

I’m sure there’s actually a smoother line, but I only used the data points I had for sure.

---

The experience needed to get to a level n from the previous level is 750+250*floor(n/2). If you look at the differences between the numbers, they follow a simple pattern: 1000, 1000, 1250, 1250, 1500, 1500... This formula was tested for levels 51 and 99, and the values matched exactly. Some of the values don't quite fit, such as that for 50, but that one looks strange anyway.

Given this, a close enough formula is 62.5x^2+750x-750. To be more exact, that equation fits for even-numbered levels, and is 62.5 points too high for odd-numbered levels, which isn't much.