Squared triangular number ( Sum of cubes ) | Function to find if the given number is sum of the cubes of first n natural numbers ; Start adding cubes of the numbers from 1 ; If sum becomes equal to s return n ; Driver code
< ? php function findS ( $ s ) { $ sum = 0 ; for ( $ n = 1 ; $ sum < $ s ; $ n ++ ) { $ sum += $ n * $ n * $ n ; if ( $ sum == $ s ) return $ n ; } return -1 ; } $ s = 9 ; $ n = findS ( $ s ) ; if ( $ n == -1 ) echo ( " - 1" ) ; else echo ( $ n ) ; ? >