CREATE TABLE table_17367 ("District" TEXT, "Vacator" TEXT, "Reason for change" TEXT, "Successor" TEXT, "Date successor seated" TEXT)

How many successors were seated in the New York 20th district?
SELECT COUNT("Successor") FROM table_17367 WHERE "District" = 'New York 20th'
SELECT COUNT("Successor") FROM "table_17367" WHERE "District" = 'New York 20th'