Stuk 55b - Letters from W. W. Rouse Ball to G. H. Hardy, with notes on the Four Digits and Four Fours Problems

Letter, 11 Sept 1918 from Rowse Ball to Hardy sent with 'a copy of what I said about the Four Digits and the Four "4s" Problems in my Recreations'; another letter, 12 Sept 1918, from Rowse Ball to Hardy on the Four Digits Problem. Paper wrapper labelled 'De 1, 2, 3, 4 problem' containing 2 folded typed sheets, with MS annotations, headed 'From my Math. Rec. [Mathematical Recreations and Essays, published by Rowse Ball in 1892]' 'Four Digits Problem' and 'Four Fours Problem'; printed sheet, 'An Extension of the Sturm-Liouville Expansion', with MS notes on back, plus another sheet ; 21 sheets of MS notes and calculations.