The National Assn. of Securities Dealers issued a series of proposals intended to strengthen the over-the-counter stock market in the aftermath of last month's crash. In particular, the ideas up for comment focus on increasing the use of computers rather than telephones in handling small orders and on expanding the commitment of dealers to provide continuous markets in stocks. There were numerous complaints in the crush of selling, particularly on Black Monday Oct. 19, that some over-the-counter dealers could not be reached by telephone or failed to provide an uninterrupted market for buy and sell orders. About 5,700 stocks that are not listed on a stock exchange are traded by competing dealers in the NASD's automated quotations, or NASDAQ, system.