<? // pentagonal, triangle and hexagonal forumla functions v1.0 function pentagonal($n) { return ( $n * ( ( 3 * $n ) - 1) ) / 2; } function triangle($n) { return ( $n * ( $n + 1 ) ) / 2; } function hexagonal($n) { return $n * ( ( 2 * $n ) - 1 ); }?>