Number of sequences which has HEAD at alternate positions to the right of the first HEAD | function to calculate total sequences possible ; Value of N is even ; Value of N is odd ; Driver code
< ? php function findAllSequence ( $ N ) { if ( $ N % 2 == 0 ) { return pow ( 2 , $ N / 2 + 1 ) + pow ( 2 , $ N / 2 ) - 2 ; } else { return pow ( 2 , ( $ N + 1 ) / 2 ) + pow ( 2 , ( $ N + 1 ) / 2 ) - 2 ; } } $ N = 2 ; echo findAllSequence ( $ N ) ; ? >