A classic (pre 1900) textbook on algebra by Chrystal has recently been scanned and made available electronically. Volume 1 is not likely to be of much interest for training purposes but chapters 23 and 24 (on combinatorics), 32 through 34 (continued fractions), and 35 (number theory), of volume 2 are. However, be warned, the scanned PDF is about 30M, so don’t try this on a slow or expensive connection!