If you expand the exponent's formula by + 1 / ( 29 + (1 / (10-Wf) )^9 ), it will apply to all warp factors except 9.6. For 9.6 there will be 1979 instead of 1909.

I developed a lot easier formula to calculate the TNG warp speeds above of Warp 9.9. (then the formula in the article.) Apart from that, the formula given in the article does not work for the canonical values and is always a bit off the mark. Warp 9,9 - canon 3053 - formula in article 3065 Warp 9,99...