Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| District | Vacator | Reason for change | Successor | Date successor seated |
| --- | --- | --- | --- | --- |
| New York 20th | Egbert Ten Eyck (J) | Lost contested election December 15, 1825 | Daniel Hugunin, Jr. (A) | Seated December 15, 1825 |
| Pennsylvania 18th | Patrick Farrelly (J) | Died January 12, 1826 | Thomas H. Sill (A) | Seated March 14, 1826 |
| Mississippi At-large | Christopher Rankin (J) | Died March 14, 1826 | William Haile (J) | Seated July 10, 1826 |
| North Carolina 8th | Willie P. Mangum (J) | Resigned March 18, 1826 | Daniel L. Barringer (J) | Seated December 4, 1826 |
| Pennsylvania 13th | Alexander Thomson (J) | Resigned May 1, 1826 | Chauncey Forward (J) | Seated December 4, 1826 |
| Ohio 10th | David Jennings (A) | Resigned May 25, 1826 | Thomas Shannon (A) | Seated December 4, 1826 |
| Kentucky 5th | James Johnson (J) | Died August 13, 1826 | Robert L. McHatton (J) | Seated December 7, 1826 |
| Pennsylvania 7th | Henry Wilson (J) | Died August 14, 1826 | Jacob Krebs (J) | Seated December 4, 1826 |
| Kentucky 12th | Robert P. Henry (J) | Died August 25, 1826 | John F. Henry (A) | Seated December 11, 1826 |
| Maine 5th | Enoch Lincoln (A) | Resigned before September 11, 1826 | James W. Ripley (J) | Seated September 11, 1826 |
Question:
Name the reason for change pennsylvania 13th
Answer:
Resigned May 1, 1826