Count of numbers of length N having prime numbers at odd indices and odd numbers at even indices | function to find total number of ways ; No of odd indices in n - digit number ; No of even indices in n - digit number ; No of ways of arranging prime number digits in odd indices ; No of ways of arranging odd number digits in even indices ; returning the total number of ways ; drive code
function find_Numb_ways ( n ) { var odd_indices = n / 2 ; var even_indices = ( n / 2 ) + ( n % 2 ) ; var arr_odd = Math . pow ( 4 , odd_indices ) ; var arr_even = Math . pow ( 5 , even_indices ) ; return arr_odd * arr_even ; } var n = 4 ; document . write ( find_Numb_ways ( n ) ) ;