The following question raised by P. C. Hammer in 1960 is answered: Let M be the set of all positive integers, ft the closure function under multiplication defined on the power set of M and c the complementation functi...The following question raised by P. C. Hammer in 1960 is answered: Let M be the set of all positive integers, ft the closure function under multiplication defined on the power set of M and c the complementation function. Do h and c generate exactly 14 distinct functions by composition in any order? Different types of sets which yield 14 distinct sets in the set of positive intergers will also be found.展开更多
基金This research s partially supported by UGC(UK)grant No.221600370.
文摘The following question raised by P. C. Hammer in 1960 is answered: Let M be the set of all positive integers, ft the closure function under multiplication defined on the power set of M and c the complementation function. Do h and c generate exactly 14 distinct functions by composition in any order? Different types of sets which yield 14 distinct sets in the set of positive intergers will also be found.