EN
We show how the idea behind a formula for π discovered by the Indian mathematician and astronomer Nilakantha (1445-1545) can be developed into a general series acceleration technique which, when applied to the Gregory-Leibniz series, gives the formula
$π = ∑_{n=0}^{∞} ((5n+3)n!(2n)!)/(2^{n-1}(3n+2)!)$
with convergence as $13.5^{-n}$, in much the same way as the Euler transformation gives
$π = ∑_{n=0}^{∞} (2^{n+1}n!n!)/(2n+1)!$
with convergence as $2^{-n}$. Similar transformations lead to other accelerated series for π, including three "BBP-like" formulas, all of which are collected in the Appendix. Optimal convergence is achieved using Chebyshev polynomials.