Type in a positive integer N and push the button "Go". The result is a list of the first 100 terms of the so-called Collatz-, Syracuse-, or 3n+1-sequence starting with your given N. For a more extensive description and a list of record calculations we refer to Eric Roosendaal's 3n+1-homepage.

If you want to see the 100-th to the 200-th term of the
Collatz-sequence type these
values in the fields preceded by "Show from" and "to".

You may want to know what happens if you change 3n+1 into 3n-1, or 5n-1, or something else. This can be effected by making a choice in the menu called "Method".

After the menu "Method" you find a second menu with the items "long" and "short". The "long" method simply carries out the Collatz-algorithm n->n/2 if n is even and n->3n+1 if n is odd. The "short" version immediately carries out a division by 2 after the n->3n+1 step. So the short version reads n->n/2 if n even and n->(3n+1)/2 if n is odd. The same principle applies to the 3n-1, 5n-1, etc. method.

FINALLY ONE WARNING. This applet can work only with numbers up to 1,000,000,000. So when you discover negative numbers in the output, the maximal size of 1,000,000,000 has been exceeded somewhere, and the results are not reliable any more.

Author: Frits Beukers, February 2002