Sum of the first N terms of the series 5 , 12 , 23 , 38. ... | Function to calculate the sum ; number of terms to be included in sum ; find the Sn
< ? php function calculateSum ( $ n ) { return 2 * ( $ n * ( $ n + 1 ) * ( 2 * $ n + 1 ) / 6 ) + $ n * ( $ n + 1 ) / 2 + 2 * ( $ n ) ; } $ n = 3 ; echo " Sum = " ? >