Summation of d * ETF ( d ) where d belongs to set of divisors of n
for ( $ j = $ i ; $ j <= $ n ; $ j += $ i ) { $ ans [ $ j ] += ( $ i * $ phi [ $ i ] ) ; } } $ answer = $ ans [ $ m ] ; $ answer = ( $ answer + 1 ) * $ m ; $ answer = ( int ) ( $ answer / 2 ) ; return $ answer ; }