Find all numbers up to N which are both Pentagonal and Hexagonal | Function to prvar numbers upto N which are both pentagonal as well as hexagonal numbers ; Calculate i - th pentagonal number ; Check if the pentagonal number pn is hexagonal or not ; Driver code
function pen_hex ( n ) { var pn = 1 ; for ( i = 1 ; i < n ; i ++ ) { pn = parseInt ( i * ( 3 * i - 1 ) / 2 ) ; if ( pn > n ) break ; var seqNum = ( 1 + Math . sqrt ( 8 * pn + 1 ) ) / 4 ; if ( seqNum == parseInt ( seqNum ) ) document . write ( pn + " " ) ; } } var N = 1000000 ; pen_hex ( N ) ;