Find sum of even index binomial coefficients | Return the sum of even index term ; Calculate value of Binomial Coefficient in bottom up manner ; Base Cases ; Calculate value using previously stored values ; finding sum of even index term . ; Driver Code
< ? php function evenSum ( $ n ) { $ C = array ( array ( ) ) ; $ i ; $ j ; for ( $ i = 0 ; $ i <= $ n ; $ i ++ ) { for ( $ j = 0 ; $ j <= min ( $ i , $ n ) ; $ j ++ ) { if ( $ j == 0 or $ j == $ i ) $ C [ $ i ] [ $ j ] = 1 ; else $ C [ $ i ] [ $ j ] = $ C [ $ i - 1 ] [ $ j - 1 ] + $ C [ $ i - 1 ] [ $ j ] ; } } $ sum = 0 ; for ( $ i = 0 ; $ i <= $ n ; $ i += 2 ) $ sum += $ C [ $ n ] [ $ i ] ; return $ sum ; } $ n = 4 ; echo evenSum ( $ n ) ; ? >