The rational iteration method by Georges Lemaitre (working papers)

In 1942, the famous astronomer and physicist Belgian Georges Lemaitre (1894-1966) published in the Bulletin of the class of Sciences of the Royal Academy of Belgium, an article in which he proposes a method that he calls "rational iteration". He rediscovers both the $\Delta^{2}$ Aitken process and the Steffensen's method. We will see how the scientific concerns of Georges Lemaitre in the year 1942 (resolutions of differential equations) have led to this rediscovery.