there could be more than 10 digits also. My main requirement is i need all the combinations to be generated. the series i found like if last (N) and last-1 (N-1) digits are interchanged, in next sequence N-2 can be incremented and generate sequence with missing numbers like in series 1,2,3,4, second sequence wil be 1,2,4,3 ( interchange last two digits). next 1,3,2,4(N-3 digit is incremented and missing numbers 2,4 are placed). it could give all the combinations. but in coding wise how to arrive i couldnt get.

pls provide procedure to generate all the combinations if input is given for @a='1,2,3,4,5,6,7'.. likewise