an iterator is referenceencapsulated in class objectthat points to link in an associated list iterator methods allow the user to move the iterator along the list and access the link currently pointed to an iterator can be used to traverse through listperforming some operation on selected links (or all linkstriangular numbers it' said that the pythagoriansa band of mathematicians in ancient greece who worked under pythagoras (of pythagorian theorem fame)felt mystical connection with the series of numbers (where the means the series continues indefinitelycan you find the next member of this seriesthe nth term in the series is obtained by adding to the previous term thus the second term is found by adding to the first term (which is )giving the third term is added to the second term (which is )giving and so on the numbers in this series are called triangular numbers because they can be visualized as triangular arrangements of objectsshown as little squares in figure finding the nth term using loop suppose you wanted to find the value of some arbitrary nth term in the seriessay the fourth term (whose value is how would you calculate itlooking at figure you might decide that the value of any term can be obtained by adding up all the vertical columns of squares in the fourth termthe first column has four little squaresthe second column has threeand so on adding + + + gives figure the triangular numbers